Analysis Of Designing A Website Using Css Computer Science Essay

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Introduction

CSS stands for the Cascading Style Sheet is a style sheet language with which a web developer can create the look and feel of his web pages. It came in 1997 but became very popular by 2000. CSS was developed to separate the design from the content in a web design. Its most common application is to style web pages written in HTML and XHTML, but the language can also be applied to any kind of XML document, including SVG and XUL. Nowadays, most of the browsers support the use of CSS Level 1, CSS Level 2 and some features of CSS Level 3.

Apparently CSS may appear tougher than plain HTML, but with Cascading Style Sheet one can simply do more with a website as it offers more options to the web developer. A CSS refers to the technical specifications of a layout. It ensures that a web page will appear exactly the way the developer has specified.

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When you create a website for your business, time and money are likely to be major concerns. Luckily, there is a web design method that can help you save time and money while also improving your visitor's experience. Cascading Style Sheets, more commonly known as CSS, has fast become the preferred web design method for the benefits it offers web designers and website visitors alike.

CSS is a language used to detail the presentation of a web page's markup language (most commonly HTML or XHTML) - such as colors, fonts, and layout. One of its key benefits is the way it allows the separation of document content (written in HTML or a similar markup language) from document presentation (written in CSS).

If you already have a website that was designed using tables, you may be reluctant to make the switch to CSS, which will require some time and effort. However, the benefits of CSS are the same for new and old websites alike.

CSS has a simple syntax and uses a number of English keywords to specify the names of various style properties.

A style sheet consists of a list of rules. Each rule or rule-set consists of one or more selectors and a declaration block. A declaration-block consists of a list of declarations in braces. Each declaration itself consists of a property, a colon (:), a value, then a semi-colon (;).[1]

In CSS, selectors are used to declare which of the markup elements a style applies to, a kind of match expression. Selectors may apply to all elements of a specific type, or only those elements that match a certain attribute; elements may be matched depending on how they are placed relative to each other in the markup code, or on how they are nested within the document object model.

Use

Prior to CSS, nearly all of the presentational attributes of HTML documents were contained within the HTML markup; all font colors, background styles, element alignments, borders and sizes had to be explicitly described, often repeatedly, within the HTML. CSS allows authors to move much of that information to a separate style sheet resulting in considerably simpler HTML markup.

Headings (h1 elements), sub-headings (h2), sub-sub-headings (h3), etc., are defined structurally using HTML. In print and on the screen, choice of font, size, color and emphasis for these elements is presentational.

Prior to CSS, document authors who wanted to assign such typographic characteristics to, say, all h2 headings had to use the HTML fontand other presentational elements for each occurrence of that heading type. The additional presentational markup in the HTML made documents more complex, and generally more difficult to maintain. In CSS, presentation is separated from structure. In print, CSS can define color, font, text alignment, size, borders, spacing, layout and many other typographic characteristics. It can do so independently for on-screen and printed views. CSS also defines non-visual styles such as the speed and emphasis with which text is read out by aural text readers. TheW3C now considers the advantages of CSS for defining all aspects of the presentation of HTML pages to be superior to other methods. It has therefore deprecated the use of all the original presentational HTML markup.

Sources

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CSS information can be provided by various sources. CSS style information can be either attached as a separate document or embedded in the HTML document. Multiple style sheets can be imported. Different styles can be applied depending on the output device being used; for example, the screen version can be quite different from the printed version, so that authors can tailor the presentation appropriately for each medium.

Priority scheme for CSS sources (from highest to lowest priority):

Author styles (provided by the web page author), in the form of:

Inline styles, inside the HTML document, style information on a single element, specified using the "style" attribute

Embedded style, blocks of CSS information inside the HTML itself

External style sheets, i.e., a separate CSS file referenced from the document

User style:

A local CSS file the user specifies with a browser option, which acts as an override applied to all documents

User agent style

Default styles applied by the user agent, i.e., the browser's default settings for element presentation

The style sheet with the highest priority controls the content display. Declarations not set in the highest priority source are passed on by a source of lower priority such as the user agent style. This process is called cascading.

One of the goals of CSS is also to allow users greater control over presentation. Someone who finds red italic headings difficult to read may apply a different style sheet. Depending on their browser and the web site, a user may choose from various style sheets provided by the designers, may remove all added style and view the site using the browser's default styling, or may override just the red italic heading style without altering other attributes.

File highlightheaders.css containing:

h1 { color: white; background-color: orange !important; }

h2 { color: white; background-color: green !important; }

Such a file is stored locally and is applicable if that has been specified in the browser options. "!important" means that it prevails over the author specifications.

Background

Style sheets have existed in one form or another since the beginnings of SGML in the 1970s. Cascading Style Sheets were developed as a means for creating a consistent approach to providing style information for web documents.

As HTML grew, it came to encompass a wider variety of stylistic capabilities to meet the demands of web developers. This evolution gave the designer more control over site appearance but at the cost of HTML becoming more complex to write and maintain. Variations in web browser implementations i.e. ViolaWWW and WorldWideWeb[3] made consistent site appearance difficult, and users had less control over how web content was displayed. Robert Cailliau wanted to separate the structure from the presentation.[3] The ideal way would be to give the user different options and transferring three different kinds of style sheets: one for printing, one for the presentation on the screen and one for the editor feature.[3]

To improve web presentation capabilities, nine different style sheet languages were proposed to the World Wide Web Consortium's (W3C) www-style mailing list. Of the nine proposals, two were chosen as the foundation for what became CSS: Cascading HTML Style Sheets (CHSS) and Stream-based Style Sheet Proposal (SSP). CHSS, a language that has some resemblance to today's CSS, was proposed by Håkon Wium Lie in October 1994. Bert Bos was working on a browser called Argo, which used its own style sheet language the SSP.[4]Lie and Yves Lafon joined Dave Raggett to expand the Arena browser for supporting CSS as a testbed application for the W3C.[5][6][7] Lie and Bos worked together to develop the CSS standard (the 'H' was removed from the name because these style sheets could also be applied to other markup languages besides HTML).[8]

Unlike existing style languages like DSSSL and FOSI, CSS allowed a document's style to be influenced by multiple style sheets. One style sheet could inherit or "cascade" from another, permitting a mixture of stylistic preferences controlled equally by the site designer and user.

Lie's proposal was presented at the "Mosaic and the Web" conference (later called WWW2) in Chicago, Illinois in 1994, and again with Bert Bos in 1995.[8] Around this time the W3C was already being established, and took an interest in the development of CSS. It organized a workshop toward that end chaired by Steven Pemberton. This resulted in W3C adding work on CSS to the deliverables of the HTML editorial review board (ERB). Lie and Bos were the primary technical staff on this aspect of the project, with additional members, including Thomas Reardon of Microsoft, participating as well. In August 1996 Netscape Communication Corporation presented an alternative style sheet language called JavaScript Style Sheets(JSSS).[8] The spec was never finished and is deprecated.[9] By the end of 1996, CSS was ready to become official, and the CSS level 1 Recommendation was published in December.

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Development of HTML, CSS, and the DOM had all been taking place in one group, the HTML Editorial Review Board (ERB). Early in 1997, the ERB was split into three working groups: HTML Working group, chaired by Dan Connolly of W3C; DOM Working group, chaired by Lauren Wood of SoftQuad; and CSS Working group, chaired by Chris Lilley of W3C.

The CSS Working Group began tackling issues that had not been addressed with CSS level 1, resulting in the creation of CSS level 2 on November 4, 1997. It was published as a W3C Recommendation on May 12, 1998. CSS level 3, which was started in 1998, is still under development as of 2009.

In 2005 the CSS Working Groups decided to enforce the requirements for standards more strictly. This meant that already published standards like CSS 2.1, CSS 3 Selectors and CSS 3 Text were pulled back from Candidate Recommendation to Working Draft level.

Difficulty with adoption

Although the CSS1 specification was completed in 1996 and Microsoft's Internet Explorer 3[8] was released in that year featuring some limited support for CSS, it was more than three years before any web browser achieved near-full implementation of the specification. Internet Explorer 5.0 for the Macintosh, shipped in March 2000, was the first browser to have full (better than 99 percent) CSS1 support[citation needed], surpassing Opera, which had been the leader since its introduction of CSS support 15 months earlier. Other browsers followed soon afterwards, and many of them additionally implemented parts of CSS2. As of August 2010, no (finished) browser has fully implemented CSS2, with implementation levels varying (seeComparison of layout engines (CSS)).

Even though early browsers such as Internet Explorer 3[8] and 4, and Netscape 4.x had support for CSS, it was typically incomplete and afflicted with serious bugs. This was a serious obstacle for the adoption of CSS.

When later 'version 5' browsers began to offer a fairly full implementation of CSS, they were still incorrect in certain areas and were fraught with inconsistencies, bugs and other quirks. The proliferation of such CSS-related inconsistencies and even the variation in feature support has made it difficult for designers to achieve a consistent appearance across platforms. Some authors resorted to workarounds such as CSS hacks and CSS filters to obtain consistent results across web browsers and platforms.

Problems with browsers' patchy adoption of CSS along with errata in the original specification led the W3C to revise the CSS2 standard into CSS2.1, which moved nearer to a working snapshot of current CSS support in HTML browsers. Some CSS2 properties that no browser successfully implemented were dropped, and in a few cases, defined behaviors were changed to bring the standard into line with the predominant existing implementations. CSS2.1 became a Candidate Recommendation on February 25, 2004, but CSS2.1 was pulled back to Working Draft status on June 13, 2005,[10] and only returned to Candidate Recommendation status on July 19, 2007.[11]

In the past, some web servers were configured to serve all documents with the filename extension .css[12] as mime type application/x-pointplus[13] rather than text/css. At the time, the Net-Scene company was selling PointPlus Maker to convert PowerPoint files into Compact Slide Show files (using a .css extension).[14]

Variations

CSS has various levels and profiles. Each level of CSS builds upon the last, typically adding new features and typically denoted as CSS1, CSS2, and CSS3. Profiles are typically a subset of one or more levels of CSS built for a particular device or user interface. Currently there are profiles for mobile devices, printers, and television sets. Profiles should not be confused with media types, which were added in CSS2.

CSS 1

The first CSS specification to become an official W3C Recommendation is CSS level 1, published in December 1996.[15] Among its capabilities are support for:

Font properties such as typeface and emphasis

Color of text, backgrounds, and other elements

Text attributes such as spacing between words, letters, and lines of text

Alignment of text, images, tables and other elements

Margin, border, padding, and positioning for most elements

Unique identification and generic classification of groups of attributes

The W3C no longer maintains the CSS1 Recommendation.[16]

CSS 2

CSS level 2 was developed by the W3C and published as a Recommendation in May 1998. A superset of CSS1, CSS2 includes a number of new capabilities like absolute, relative, and fixed positioning of elements and z-index, the concept of media types, support for aural style sheets and bidirectional text, and new font properties such as shadows. The W3C maintains the CSS2 Recommendation.[17]

CSS level 2 revision 1 or CSS 2.1 fixes errors in CSS2, removes poorly-supported features and adds already-implemented browser extensions to the specification. While it was aCandidate Recommendation for several months, on June 15, 2005 it was reverted to a working draft for further review.[18] It was returned to Candidate Recommendation status on 19 July 2007.

CSS 3

CSS level 3 has been under development since December 15, 2005.[19] [20] The W3C maintains a CSS3 progress report. CSS3 is modularized and consists of several separate recommendations. The W3C CSS3 Roadmap provides a summary and introduction.[21]

Why CSS?

CSS is designed primarily to enable the separation of document content (written in HTML or a similar markup language) from document presentation, including elements such as the layout, colors, and fonts. This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple pages to share formatting, and reduce complexity and repetition in the structural content (such as by allowing for tableless web design). CSS can also allow the same markup page to be presented in different styles for different rendering methods, such as on-screen, in print, by voice (when read out by a speech-based browser or screen reader) and on Braille-based, tactile devices. While the author of a document typically links that document to a CSS style sheet, readers can use a different style sheet, perhaps one on their own computer, to override the one the author has specified.

CSS specifies a priority scheme to determine which style rules apply if more than one rule matches against a particular element. In this so-called cascade, priorities or weights are calculated and assigned to rules, so that the results are predictable.

The CSS specifications are maintained by the World Wide Web Consortium (W3C). 

Consistency

By making one change to your website's CSS style sheet, you can automatically make it to every page of your website. The bigger your website, the more time CSS saves you. And not only does CSS save time, it also ensures that your web pages have consistent styling throughout your site.

Bandwidth Reduction

When CSS separates your website's content from its design language, you dramatically reduce your file transfer size. Your CSS document will be stored externally, and will be accessed only once when a visitor requests your website. In contrast, when you create a website using tables, every page of your website will be accessed with each visit. Your reduced bandwidth needs will result in a faster load time and could cut your web hosting costs.

Search Engines

CSS is considered a clean coding technique, which means search engines won't have to struggle to "read" its content. Also, using CSS will leave your website with more content than code - and content is critical to your search engine success.

Browser Compatibility

The recent arrival of Google® Chrome is further evidence that today's Internet users have more browser options than ever before, which makes browser compatibility a major issue for your website. CSS style sheets increase your website's adaptability and ensure that more visitors will be able to view your website in the way you intended.

Viewing Options

Another common web design concern is the increasing need to make websites available for different media. CSS can help you tackle this challenge by allowing the same markup page to be presented in different viewing styles -- for example, you may create a separate style sheet for print or for a mobile device.

With so many advantages to offer, CSS is a wise choice for web design. If you're interested in making your website load faster, look better and rank higher, consider using CSS to create a new website or improve an existing website.

Critical Analysis of CSS

But out of all things, why should one opt for designing his website using CSS? Here are some advantages of CSS for you:

Separating style from content

The main benefit in CSS, is that it manages to separate the style from the content on your web page. If you are used to using HTML, you'll have noticed, that HTML can do both style and content. With a FONT-tag, and some artistic sense, you can make a HTML page quite stylish.

What CSS does, is that it handles the style of your web page, and lets HTML do the content. Why is this good?

First of all, the stylish capabilities in HTML are quite limited. Secondly, with the use of an external style sheet, you are able to alter you entire site style, by only editing one single file!

As an example of the above, let's say you wanted to change your site from using Times New Roman to Arial. With 'old-fashioned' HTML, you would have to alter the FONT tag, on each and every page. With CSS, you would just need to alter the style sheet, and then all pages would be using Arial.

Even though trends are towards decentralization, you actually make things easier, more efficient, and save time, by centralizing your style into one single style sheet.

Improved usability

If you started using style sheets extensively, your site would automatically become more usable.

By removing all nasty BODY-attributes and font tags et. al. from your HTML pages, and moving these into a nice single external style sheet, your HTML pages will turn smaller in size, and the style sheet would only need to be downloaded once (as further requests would later be taken from the users cache), and thus your site would load faster.

With the use of CSS, it's also important to remember that unlike other nice web technologies (e.g. ActiveX, JavaScript, VBScript etc.), your users do not loose functionality, if their chosen browser does not support CSS. They will simply just get plain text -- your raw content.

Also remembering that the FONT-tag, and many BODY-attributes are browser specific your site also becomes more easier to read and understand for browsers.

Improved Search Engine Results

With use of CSS, you can keep your HTML code much cleaner. As a result search engine bots do not have to separate the real content from the junk code. You are also free to put any content anywhere in your document with CSS. This will aid the search engine crawlers to identify the important content first.

Sites Load Faster

As the style sheets are lighter, it will enable the websites to load faster. Since table layouts are no longer required in CSS, the sites take up less memory and load faster. The users will find it easier to view a site designed using CSS as it will load in a fast pace and can be swiftly navigated from one page to other.

Design Separated from Content

A web designer has more control over a website with CSS as a style sheet can be linked to all your web documents. For a slight modification, what you have to do is edit a single file, just the style sheet. Information related to layout, positioning, style, font and color are all put in a style sheet for the entire site.

Displayed on Various Media

A web designer has great flexibility in presenting the content. Different style sheets can be used for different media without even the user knowing it. Style sheets can be made for different media like the printer and PDA.

Compatibility with Browsers

Adhering to the web standards set by W3C, a designer is making it obvious that the content of a site is validated in all browsers. But with the introduction of a new browsers, it is not possible to test a website for all probable browsers. But if the coding is done following to a standard, a major part of the job is already done.

Use CSS to discover its full potential. Flexibility is the most beneficial features of using Cascading Style Sheets. Start using it and get benefited by its multiple advantages.

Issues to be addressed

Though CSS has its strengths, it also has its weaknesses. Web professionals that used CSS as their base for layout designing and editing have also cited some drawbacks upon relying heavily on the style sheet language. Here are a short list of the some disadvantages of using pure CSS on web layouts and designs.

* Collapsing Margins - Margin collapsing is, while well-documented and useful, also complicated and is frequently not expected by authors, and no simple side-effect-free way is available to control it.

* No Expressions - There is currently no ability to specify property values as simple expressions (such as margin-left: 10% - 3em + 4px;). This is useful in a variety of cases, such as calculating the size of columns subject to a constraint on the sum of all columns.

* Lack of Variables - CSS contains no variables. This makes it necessary to do a "replace-all" when one desires to change a fundamental constant, such as the color scheme or various heights and widths.

* Inconsistent Browser Support - Different browsers will render CSS layout differently as a result of browser bugs or lack of support for CSS features. Numerous so-called CSS "hacks" must be implemented to achieve consistent layout among the most popular or commonly used browsers. Pixel precise layouts can sometimes be impossible to achieve across browsers.

* Vertical Control Limitation - While horizontal placement of elements is generally easy to control, vertical placement is frequently unintuitive, convoluted, or impossible. Simple tasks, such as centering an element vertically or getting a footer to be placed no higher than bottom of viewport, either require complicated and unintuitive style rules, or simple but widely unsupported rules.

* Control of Element Shapes - CSS currently only offers rectangular shapes. Rounded corners or other shapes may require non-semantic markup. However, this is addressed in the working draft of the CSS3 backgrounds module.

* Poor Layout Controls for Flexible Layouts - While new additions to CSS3 provide a stronger, more robust layout feature-set, CSS is still very much rooted as a styling language, not a layout language.

* Lack of Column Declaration - While possible in current CSS, layouts with multiple columns can be complex to implement. With the current CSS, the process is often done using floating elements which are often rendered differently by different browsers, different computer screen shapes, and different screen ratios set on standard monitors.

Implementation

An implementation of the proposed scheme is planned. Most of the code can and should be put into the common code library so that browsers easily will be able to support style sheets.

Conclusion

Though a number of difficulties, drawbacks, and disadvantages were found through use of "pure" CSS, its usefulness in web design is still apparent in other ways. Because of its accessibility, web content for mobiles phones and PDAs became accessible because of CSS. CSS consumes lesser bandwidth. And with CSS, virtually all of the layout information resides in one place: the CSS document. Because the layout information is centralized, these changes can be made quickly and globally by default.