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Wednesday, December 22, 2010

Theory of relativity

The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word "relativity" is sometimes used in reference to Galilean invariance.
The term "theory of relativity" was based on the expression "relative theory" (German: Relativtheorie) used by Max Planck in 1906, who emphasized how the theory uses the principle of relativity. In the discussion section of the same paper Alfred Bucherer used for the first time the expression "theory of relativity" (German: Relativitätstheorie).




Scope

The theory of relativity enriched physics and astronomy during the 20th century. When first published, relativity superseded a 200-year-old theory of mechanics elucidated by Isaac Newton. It changed perceptions.

For example, it overturned the concept of motion from Newton's day, into all motion is relative. Time was no longer uniform and absolute, as related to everyday experience. Furthermore, no longer could physics be understood as space by itself, and time by itself. Instead, an added dimension had to be taken into account with curved space-time. Time now depended on velocity, and contraction became a fundamental consequence at appropriate speeds.

In the field of microscopic physics, relativity catalyzed and added an essential depth of knowledge to the science of elementary particles and their fundamental interactions, along with introducing the nuclear age. With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves.
Two theory view

The theory of relativity was representative of more than a single new physical theory. It affected the theories and methodologies across all the physical sciences. However, as stated above, this is more likely perceived as two separate theories. There are some related explanations for this. First, special relativity was published in 1905, and the final form of general relativity was published in 1916.

Second, special relativity fits with and solves for elementary particles and their interactions, whereas general relativity solves for the cosmological and astrophysical realm (including astronomy).

Third, special relativity was widely accepted in the physics community by 1920. This theory rapidly became a notable and necessary tool for theorists and experimentalists in the new fields of atomic physics, nuclear physics, and quantum mechanics. Conversely, general relativity did not appear to be as useful. There had appeared to be little applicability for experimentalists as most applications were for astronomical scales. It seemed limited to only making minor corrections to predictions of Newtonian gravitation theory. Its impact was not apparent until the 1930s.

Finally, the mathematics of general relativity appeared to be incomprehensibly dense. Consequently, only a small number of people in the world, at that time, could fully understand the theory in detail. This remained the case for the next 40 years. Then, at around 1960 a critical resurgence in interest occurred which has resulted in making general relativity central to physics and astronomy. New mathematical techniques applicable to the study of general relativity substantially streamlined calculations. From this, physically discernible concepts were isolated from the mathematical complexity. Also, the discovery of exotic astronomical phenomena in which general relativity was crucially relevant, helped to catalyze this resurgence. The astronomical phenomena included quasars (1963), the 3-kelvin microwave background radiation (1965), pulsars (1967), and the discovery of the first black hole candidates

Monday, December 13, 2010

HTML

HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. A markup language is a set of markup tags, and HTML uses markup tags to describe web pages.

HTML is written in the form of HTML elements consisting of "tags" surrounded by angle brackets (like <html>) within the web page content. HTML tags normally come in pairs like <b> and </b>. The first tag in a pair is the start tag, the second tag is the end tag (they are also called opening tags and closing tags).

The purpose of a web browser is to read HTML documents and display them as web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page.

HTML elements form the building blocks of all websites. HTML allows images and objects to be embedded and can be used to create interactive forms. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. It can embed scripts in languages such as JavaScript which affect the behavior of HTML webpages.
HTML can also be used to include Cascading Style Sheets (CSS) to define the appearance and layout of text and other material. The W3C, maintainer of both HTML and CSS standards, encourages the use of CSS over explicit presentational markup

Tuesday, November 30, 2010

Website

A website (also spelled Web site) is a collection of related web pages, images, videos or other digital assets that are addressed relative to a common Uniform Resource Locator (URL), often consisting of only the domain name, or the IP address, and the root path ('/') in an Internet Protocol-based network. A web site is hosted on at least one web server, accessible via a network such as the Internet or a private local area network.

A web page is a document, typically written in plain text interspersed with formatting instructions of Hypertext Markup Language (HTML, XHTML). A web page may incorporate elements from other websites with suitable markup anchors.

Web pages are accessed and transported with the Hypertext Transfer Protocol (HTTP), which may optionally employ encryption (HTTP Secure, HTTPS) to provide security and privacy for the user of the web page content. The user's application, often a web browser, renders the page content according to its HTML markup instructions onto a display terminal.

All publicly accessible websites collectively constitute the World Wide Web.

The pages of a website can usually be accessed from a simple Uniform Resource Locator (URL) called the homepage. The URLs of the pages organize them into a hierarchy, although hyperlinking between them conveys the reader's perceived site structure and guides the reader's navigation of the site.

Some websites require a subscription to access some or all of their content. Examples of subscription websites include many business sites, parts of news websites, academic journal websites, gaming websites, message boards, web-based e-mail, social networking websites, websites providing real-time stock market data, and websites providing various other services (e.g. websites offering storing and/or sharing of images, files and so forth).


History

The World Wide Web (WWW) was created in 1989 by CERN physicist Tim Berners-Lee.[3] On 30 April 1993, CERN announced that the World Wide Web would be free to use for anyone.[4] Before the introduction of HTML and HTTP, other protocols such as file transfer protocol and the gopher protocol were used to retrieve individual files from a server. These protocols offer a simple directory structure which the user navigates and chooses files to download. Documents were most often presented as plain text files without formatting or were encoded in word processor formats.
Overview

Organized by function, a website may be

    * a personal website
    * a commercial website
    * a government website
    * a non-profit organization website

It could be the work of an individual, a business or other organization, and is typically dedicated to some particular topic or purpose. Any website can contain a hyperlink to any other website, so the distinction between individual sites, as perceived by the user, may sometimes be blurred.

Websites are written in, or dynamically converted to, HTML (Hyper Text Markup Language) and are accessed using a software interface classified as a user agent. Web pages can be viewed or otherwise accessed from a range of computer-based and Internet-enabled devices of various sizes, including desktop computers, laptops, PDAs and cell phones.

A website is hosted on a computer system known as a web server, also called an HTTP server, and these terms can also refer to the software that runs on these systems and that retrieves and delivers the web pages in response to requests from the website users. Apache is the most commonly used web server software (according to Netcraft statistics) and Microsoft's Internet Information Server (IIS) is also commonly used.
Static website

A static website is one that has web pages stored on the server in the format that is sent to a client web browser. It is primarily coded in Hypertext Markup Language (HTML).

Simple forms or marketing examples of websites, such as classic website, a five-page website or a brochure website are often static websites, because they present pre-defined, static information to the user. This may include information about a company and its products and services via text, photos, animations, audio/video and interactive menus and navigation.

This type of website usually displays the same information to all visitors. Similar to handing out a printed brochure to customers or clients, a static website will generally provide consistent, standard information for an extended period of time. Although the website owner may make updates periodically, it is a manual process to edit the text, photos and other content and may require basic website design skills and software.

In summary, visitors are not able to control what information they receive via a static website, and must instead settle for whatever content the website owner has decided to offer at that time.

They are edited using four broad categories of software:

    * Text editors, such as Notepad or TextEdit, where content and HTML markup are manipulated directly within the editor program
    * WYSIWYG offline editors, such as Microsoft FrontPage and Adobe Dreamweaver (previously Macromedia Dreamweaver), with which the site is edited using a GUI interface and the final HTML markup is generated automatically by the editor software
    * WYSIWYG online editors which create media rich online presentation like web pages, widgets, intro, blogs, and other documents.
    * Template-based editors, such as Rapidweaver and iWeb, which allow users to quickly create and upload web pages to a web server without detailed HTML knowledge, as they pick a suitable template from a palette and add pictures and text to it in a desktop publishing fashion without direct manipulation of HTML code.

Dynamic website

A dynamic website is one that changes or customizes itself frequently and automatically, based on certain criteria.

Dynamic websites can have two types of dynamic activity: Code and Content. Dynamic code is invisible or behind the scenes and dynamic content is visible or fully displayed.
Dynamic code

The first type is a web page with dynamic code. The code is constructed dynamically on the fly using active programming language instead of plain, static HTML.

A website with dynamic code refers to its construction or how it is built, and more specifically refers to the code used to create a single web page. A dynamic web page is generated on the fly by piecing together certain blocks of code, procedures or routines. A dynamically-generated web page would call various bits of information from a database and put them together in a pre-defined format to present the reader with a coherent page. It interacts with users in a variety of ways including by reading cookies recognizing users' previous history, session variables, server side variables etc., or by using direct interaction (form elements, mouse overs, etc.). A site can display the current state of a dialogue between users, monitor a changing situation, or provide information in some way personalized to the requirements of the individual user.
Dynamic content

The second type is a website with dynamic content displayed in plain view. Variable content is displayed dynamically on the fly based on certain criteria, usually by retrieving content stored in a database.

A website with dynamic content refers to how its messages, text, images and other information are displayed on the web page, and more specifically how its content changes at any given moment. The web page content varies based on certain criteria, either pre-defined rules or variable user input. For example, a website with a database of news articles can use a pre-defined rule which tells it to display all news articles for today's date. This type of dynamic website will automatically show the most current news articles on any given date. Another example of dynamic content is when a retail website with a database of media products allows a user to input a search request for the keyword Beatles. In response, the content of the web page will spontaneously change the way it looked before, and will then display a list of Beatles products like CD's, DVD's and books.
Purpose of dynamic websites

The main purpose of a dynamic website is automation. A dynamic website can operate more effectively, be built more efficiently and is easier to maintain, update and expand. It is much simpler to build a template and a database than to build hundreds or thousands of individual, static HTML web pages.
Software systems

There is a wide range of software systems, such as ANSI C servlets), Java Server Pages (JSP), the PHP and Perl programming languages, ASP.NET, Active Server Pages (ASP), YUMA and ColdFusion (CFML) that are available to generate dynamic web systems and dynamic sites. Sites may also include content that is retrieved from one or more databases or by using XML-based technologies such as RSS.

Static content may also be dynamically generated either periodically, or if certain conditions for regeneration occur (cached) in order to avoid the performance loss of initiating the dynamic engine on a per-user or per-connection basis.

Plug ins are available to expand the features and abilities of web browsers, which use them to show active content, such as Microsoft Silverlight, Adobe Flash, Adobe Shockwave or applets written in Java. Dynamic HTML also provides for user interactivity and realtime element updating within web pages (i.e., pages don't have to be loaded or reloaded to effect any changes), mainly using the Document Object Model (DOM) and JavaScript, support which is built-in to most modern web browsers.

Turning a website into an income source is a common practice for web developers and website owners. There are several methods for creating a website business which fall into two broad categories, as defined below.
 Content-based sites

Some websites derive revenue by selling advertising space on the site (see Contextual advertising).
 Product- or service-based sites

Some websites derive revenue by offering products or services for sale. In the case of e-commerce websites, the products or services may be purchased at the website itself, by entering credit card or other payment information into a payment form on the site. While most business websites serve as a shop window for existing brick and mortar businesses, it is increasingly the case that some websites are businesses in their own right; that is, the products they offer are only available for purchase on the web.

Websites occasionally derive income from a combination of these two practices. For example, a website such as an online auctions website may charge the users of its auction service to list an auction, but also display third-party advertisements on the site, from which it derives further income.
Spelling

The form "website" has become the standard spelling, but previously "Web site" (capitalised) and "web site" were also widely used. Some academia, some large book publishers, and some dictionaries still use "Web site", reflecting the origin of the term in the proper name World Wide Web. There has also been similar debate regarding related terms such as web page, webmaster, and webcam.

Among leading style guides, the Reuters style guide , the Chicago Manual of Style , and the AP Stylebook (since April 2010)  all recommend "website".

Among leading dictionaries and encyclopaedias, the Canadian Oxford Dictionary prefers "website", and the Oxford English Dictionary changed to "website" in 2004.. Wikipedia also uses "website", but Encyclopædia Britannica  (including its Merriam-Webster subsidiary ) uses "Web site".

Among leading language-usage commentators, Garner's Modern American Usage acknowledges that "website" is the standard form , but Bill Walsh, of the Washington Post, argues for using "Web site" in his books and on his website  (however, the Washington Post itself uses "website" ).

Among major internet technology companies, Microsoft uses "website" and occasionally "web site" , Apple uses "website" , and Google uses "website".

Monday, November 29, 2010

Web design

Web design is a broad term used to encompass the way that content (usually hypertext or hypermedia) that are delivered to an end-user through the World Wide Web, using a web browser or other web-enabled software is displayed. The intent of web design is to create a website—a collection of online content including documents and applications that reside on a web server/servers. The website may include text, images, sounds and other content, and may be interactive.

Overview

Web design involves the structure of the website including the information architecture (navigation schemes and naming conventions), the layout or the pages (wireframes or page schematics are created to show consistent placement of items including functional features), and the conceptual design with branding.
All websites should begin with a clear strategy so that it is apparent what they are trying to achieve. The strategy then enables the design to fulfill defined goals.

Content

Such elements as text, forms, images (GIFs, JPEGs, Portable Network Graphics) and video can be placed on the page using HTML/XHTML/XML tags. Older browsers may require Plug-ins such as Adobe Flash, QuickTime, Java run-time environment, etc. to display some media, which are embedded into web page by using HTML/XHTML tags.

Improvements in browsers' compliance with W3C standards prompted a widespread acceptance and usage of XHTML/XML in conjunction with Cascading Style Sheets (CSS) to position and manipulate web page elements and objects.

Typically web pages are classified as static or dynamic:

    * Static pages don’t change content and layout with every request unless a human (web master/programmer) manually updates the page. A simple HTML page is an example of static content.
    * Dynamic pages adapt their content and/or appearance depending on end-user’s input/interaction or changes in the computing environment (user, time, database modifications, etc.) Content can be changed on the client side (end-user's computer) by using client-side scripting languages (JavaScript, JScript, Actionscript, etc.) to alter DOM elements (DHTML). Dynamic content is often compiled on the server utilizing server-side scripting languages (Perl, PHP, ASP, JSP, ColdFusion, etc.). Both approaches are usually used in complex applications.

With growing specialization in the information technology field there is a strong tendency to distinguish between web design and web development.   Web design is a kind of graphic design intended for the development and styling of objects of the Internet's information environment to provide them with high-end consumer features and aesthetic qualities.


This definition separates web design from web programming, emphasizing the functional features of a web site, as well as positioning web design as a kind of graphic design. The process of designing web pages, web sites, web applications or multimedia for the Web may utilize multiple disciplines, such as animation, authoring, communication design, corporate identity, graphic design, human-computer interaction, information architecture, interaction design, marketing, photography, search engine optimization and typography.

    * Markup languages (such as HTML, XHTML and XML)
    * Style sheet languages (such as CSS and XSL)
    * Client-side scripting (such as JavaScript)
    * Server-side scripting (such as PHP and ASP)
    * Database technologies (such as MySQL and PostgreSQL)
    * Multimedia technologies (such as Flash and Silverlight)

Web pages and websites can be static pages, or can be programmed to be dynamic pages that automatically adapt content or visual appearance depending on a variety of factors, such as input from the end-user, input from the webmaster or changes in the computing environment (such as the site's associated database having been modified).

Accessible web design

To be accessible, web pages and sites must conform to certain accessibility principles. These accessibility principles are known as the WCAG when talking about content. These can be grouped into the following main areas.

    * Use semantic markup that provides a meaningful structure to the document (i.e. web page)
    * Semantic markup also refers to semantically organizing the web page structure and publishing web services description accordingly so that they can be recognized by other web services on different web pages. Standards for semantic web are set by IEEE
    * Use a valid markup language that conforms to a published DTD or Schema
    * Provide text equivalents for any non-text components (e.g. images, multimedia)
    * Use hyperlinks that make sense when read out of context. (e.g. avoid "Click Here")


Website accessibility is also changing as it is impacted by Content Management Systems that allow changes to be made to webpages without the need of obtaining web-based programming language knowledge.

It is very important that several different components of web development and interaction can work together in order for the Web to be accessible to people with disabilities. These components include:

    * content - the information in a web page or web application, including:
          o natural information such as text, images, and sounds
          o code or markup that defines structure, presentation, etc.
    * Web browsers, media players, and other "user agents"
    * assistive technology, in some cases - screen readers, alternative keyboards, switches, scanning software, etc.
    * users' knowledge, experiences, and in some cases, adaptive strategies using the Web
    * developers - designers, coders, authors, etc., including developers with disabilities and users who contribute content
    * authoring tools - software that creates web sites
    * evaluation tools - web accessibility evaluation tools, HTML validators, CSS validators, etc.

History

Tim Berners-Lee published what is considered to be the first website in August 1991. Berners-Lee was the first to combine Internet communication (which had been carrying email and the Usenet for decades) with hypertext (which had also been around for decades, but limited to browsing information stored on a single computer, such as interactive CD-ROM design). Websites are written in a markup language called HTML, and early versions of HTML were very basic, only giving a website's basic structure (headings and paragraphs), and the ability to link using hypertext. This was new and different from existing forms of communication - users could easily navigate to other pages by following hyperlinks from page to page.

As the Web and web design progressed, the markup language changed to become more complex and flexible, giving the ability to add objects like images and tables to a page. Features like tables, which were originally intended to be used to display tabular information, were soon subverted for use as invisible layout devices. With the advent of Cascading Style Sheets (CSS), table-based layout is commonly regarded as outdated. Database integration technologies such as server-side scripting and design standards like W3C further changed and enhanced the way the Web is made. As times change, websites are changing the code on the inside and visual design on the outside with ever-evolving programs and utilities.

With the progression of the Web, tens of thousands of web design companies have been established around the world to serve the growing demand for such work. As with much of the information technology industry, many web design companies have been established in technology parks in the developing world as well as many Western design companies setting up offices in countries such as India, Romania, and Russia to take advantage of the relatively lower labor rates found in such countries.

Website planning

Purposing web design is a complex, but essential ongoing activity. Before creating and uploading a website, it is important to take the time to plan exactly what is needed in the website. Thoroughly considering the audience or target market, as well as defining the purpose and deciding what content will be developed, are extremely important.

Context

Web design is similar (in a very simplistic way) to traditional print publishing. Every website is an information display container, just as a book; and every web page is like the page in a book. However, web design uses a framework based on digital code and display technology to construct and maintain an environment to distribute information in multiple formats. Taken to its fullest potential, web design is undoubtedly the most sophisticated and increasingly complex method to support communication in today's world.

Purpose

It is essential to define the purpose of the website as one of the first steps in the planning process. A purpose statement should show focus based on what the website will accomplish and what the users will get from it. A clearly defined purpose will help the rest of the planning process as the audience is identified and the content of the site is developed. Setting short and long term goals for the website will help make the purpose clear and plan for the future when expansion, modification, and improvement will take place. Setting a goal practices and measurable objectives should be identified to track the progress of the site and determine success.

Audience

Defining the audience is a key step in the website planning process. The audience is the group of people who are expected to visit your website – the market being targeted. These people will be viewing the website for a specific reason and it is important to know exactly what they are looking for when they visit the site. A clearly defined purpose or goal of the site as well as an understanding of what visitors want to do or feel when they come to your site will help to identify the target audience. Upon considering who is most likely to need or use the content, a list of characteristics common to the users such as:
  • Audience Characteristics
  • Information Preferences
  • Computer Specifications
  • Web Experience
Taking into account the characteristics of the audience will allow an effective website to be created that will deliver the desired content to the target audience.

Content

Content evaluation and organization requires that the purpose of the website be clearly defined. Collecting a list of the necessary content then organizing it according to the audience's needs is a key step in website planning. In the process of gathering the content being offered, any items that do not support the defined purpose or accomplish target audience objectives should be removed. It is a good idea to test the content and purpose on a focus group and compare the offerings to the audience needs. The next step is to organize the basic information structure by categorizing the content and organizing it according to user needs. Each category should be named with a concise and descriptive title that will become a link on the website. Planning for the site's content ensures that the wants or needs of the target audience and the purpose of the site will be fulfilled.

Compatibility and restrictions

Because of the market share of modern browsers (depending on your target market), the compatibility of your website with the viewers is restricted. For instance, a website that is designed for the majority of websurfers will be limited to the use of valid XHTML 1.0 Strict or older, Cascading Style Sheets Level 1, and 1024x768 display resolution. This is because Internet Explorer is not fully W3C standards compliant with the modularity of XHTML 1.1 and the majority of CSS beyond 1. A target market of more alternative browser (e.g. Firefox, Safari and Opera) users allow for more W3C compliance and thus a greater range of options for a web designer.

Another restriction on webpage design is the use of different image file formats. The majority of users can support GIF, JPEG, and PNG (with restrictions). Again Internet Explorer is the major restriction here, not fully supporting PNG's advanced transparency features, resulting in the GIF format still being the most widely used graphic file format for transparent images.

Many website incompatibilities go unnoticed by the designer and unreported by the users. The only way to be certain a website will work on a particular platform is to test it on that platform.

Planning documentation

Documentation is used to visually plan the site while taking into account the purpose, audience and content, to design the site structure, content and interactions that are most suitable for the website. Documentation may be considered a prototype for the website – a model which allows the website layout to be reviewed, resulting in suggested changes, improvements and/or enhancements. This review process increases the likelihood of success of the website.

The first step may involve information architecture in which the content is categorized and the information structure is formulated. The information structure is used to develop a document or visual diagram called a site map. This creates a visual of how the web pages or content will be interconnected, and may help in deciding what content will be placed on what pages.

In addition to planning the structure, the layout and interface of individual pages may be planned using a storyboard. In the process of storyboarding, a record is made of the description, purpose and title of each page in the site, and they are linked together according to the most effective and logical diagram type. Depending on the number of pages required for the website, documentation methods may include using pieces of paper and drawing lines to connect them, or creating the storyboard using computer software.

Some or all of the individual pages may be designed in greater detail as a website wireframe, a mock up model or comprehensive layout of what the page will actually look like. This is often done in a graphic program, or layout design program. The wireframe has no working functionality, only planning, though it can be used for selling ideas to other web design companies.

Website design

Web design is different than traditional print publishing. Every website is an information display container, just as a book is a container; and every web page is like the page in a book. However the end size and shape of the web page is not known to the web designer, whereas the print designer will know exactly what size paper he will be printing on.

For the typical web sites, the basic aspects of design are:

    * The content: the substance, and information on the site should be relevant to the site and should target the area of the public that the website is concerned with.
    * The usability: the site should be user-friendly, with the interface and navigation simple and reliable.
    * The appearance: the graphics and text should include a single style that flows throughout, to show consistency. The style should be professional, appealing and relevant.
    * The structure: of the web site as a whole.


A web site typically consists of text, images, animation and /or video. The first page of a web site is known as the Home page or Index Page. Some web sites use what is commonly called a Splash Page. Splash pages might include a welcome message, language or region selection, or disclaimer, however search engines, in general, favor web sites that don't do this which has caused these types of pages to fall out of favor. Each web page within a web site is a file which has its own URL. After each web page is created, they are typically linked together using a navigation menu composed of hyperlinks.

Once a web site is completed, it must be published or uploaded in order to be viewable to the public over the internet. This may be done using an FTP client.

Multidisciplinary requirements

Web site design crosses multiple disciplines of multiple information systems, information technology, marketing, and communication design. The web site is an information system whose components are sometimes classified as front-end and back-end. The observable content (e.g. page layout, user interface, graphics, text, audio) is known as the front-end. The back-end comprises the organization and efficiency of the source code, invisible scripted functions, and the server-side components that process the output from the front-end. Depending on the size of a web development project, it may be carried out by a multi-skilled individual (sometimes called a web master), or a project manager may oversee collaborative design between group members with specialized skills.

Issues

By its very nature, web design is conflicted, involving rigid technical conformance and personal creative balance. Rapid technological change complicates acquiring and deploying suitable resources to maintain web presence.

Environment

Layout is a double edged sword: on the one hand, it is the expression of a framework that actively shapes the web designer. On the other hand, as the designer adapts that framework to projects, layout is the means of content delivery. Publishing a web engages communication throughout the production process as well as within the product created. Publication implies adaptation of culture and content standards. Web design incorporates multiple intersections between many layers of technical and social understanding, demanding creative direction, design element structure, and some form of social organization. Differing goals and methods resolve effectively in successful deployment of education, software and team management during the design process. However, many competing and evolving platforms and environments challenge acceptance, completion and continuity of every design product.

Collaboration

Early web design was less integrated with companies’ advertising campaigns, customer transactions, extranets, intranets and social networking. Web sites were seen largely as static online brochures or database connection points, disconnected from the broader scopes of a business or project. Many web sites are still disconnected from the broader project scope. As a result, many web sites are needlessly difficult to use, indirect in their way of communicating, and suffer from a 'disconnected' or ineffective bureaucratic information architecture.

Form versus function


A web developer may pay more attention to how a page looks while neglecting other copywriting and search engine optimization functions such as the readability of text, the ease of navigating the site, or how easily the visitors are going to find the site. As a result, the designers may end up in disputes where some want more decorative graphics at the expense of keyword-rich text, bullet lists, and text links. Assuming a false dichotomy that form and function are mutually exclusive overlooks the possibility of integrating multiple disciplines for a collaborative and synergistic solution. In many cases form follows function. Because some graphics serve communication purposes in addition to aesthetics, how well a site works may depend on the graphic design ideas as well as the professional writing considerations.

When using a lot of graphics, or sending a lot of instructions to the end client computer, a web page may load slowly, often irritating the user. This has become less of a problem as the internet has evolved with high-speed internet and the use of vector graphics. However there is still an ongoing engineering challenge to increase bandwidth and an artistic challenge to minimize the amount of graphics and their file sizes. This challenge is compounded since increased bandwidth encourages more graphics with larger file sizes.

Layout

Layout types

Layout refers to the dimensioning of content in a device display, and the delivery of media in a content related stream. Web design layouts result in visual content frameworks: these frameworks can be fixed, they can use units of measure that are relative, or they can provide fluid layout with proportional dimensions. The deployment flowchart (a useful tool on any design project) should address content layout. Many units of measure exist, but here are some popular dimension formats:

    * Pixel measure results in fixed or static content
    * Em measure results in proportional content that is relative to font-size
    * Percent measure results in fluid content that shrinks and grows to "fit" display windows

Proportional, liquid and hybrid layout are also referred to as dynamic design. Hybrid layout incorporates any combination of fixed, proportional or fluid elements within (or pointing to) a single page. The hybrid web design framework is made possible by digital internet conventions generally prescribed by the W3C. If any layout does not appear as it should, it is very likely that it does not conform to standard design principles, or that those standards conflict with standard layout elements. Current knowledge of standards is essential to effective hybrid design.

The earliest web pages used fixed layouts without exception. In many business pages fixed layouts are preferred today as they easily contain static tabled information. Fixed layout enforces device display convention, as viewers must set their display to at least a certain width to easily view content. This width can include display of corporate logos, cautions, advertisements and any other target content. Design frameworks for fixed layout may need to include coding for multiple display devices.

Hybrid design maintains most static content control, but is adapted to textual publishing, and for readers, to conventional (printed) display. Hybrid layouts are generally easy on the eye and are found on most sites that distribute traditional images and text to readers. For some sites, hybrid design makes an otherwise cold text column appear warm and balanced. A good example of hybrid layout is Wordpress, where liquid design is now optional, and movie and auditory media is stretching the envelope.

Fluid design is useful where content is delivered to an 'unknown device' population. Appropriate liquid code displays images, text and spaces proportional to display size. Someone with a handheld can see view and interact with the same content as someone using a large desktop monitor. However, scaling of content for a variety of devices has more recently evolved with modern web browsers, allowing users to see the same layout across all devices.

Layout concerns


Friday, November 26, 2010

Forms of pollution

The major forms of pollution are listed below along with the particular pollutants relevant to each of them:

    * Air pollution, the release of chemicals and particulates into the atmosphere. Common gaseous air pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight. Particulate matter, or fine dust is characterized by their micrometre size PM10 to PM2.5.

    * Light pollution, includes light trespass, over-illumination and astronomical interference.
    * Littering
    * Noise pollution, which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.
    * Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE, herbicides, pesticides and chlorinated hydrocarbons.
    * Radioactive contamination, resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment. (See alpha emitters and actinides in the environment.)
    * Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.
    * Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash or municipal solid waste.
    * Water pollution, by the release of waste products and contaminants into surface runoff into river drainage systems, leaching into groundwater, liquid spills, wastewater discharges, eutrophication and littering.