Accessible Code for Website design

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Accessible Website design is the art of creating web pages that are accessible to everyone, using any device. It is especially important so that people with disabilities - whether due to accident, disease or old age - can access the information in Web pages and be able to navigate through the website.

To be accessible, web pages and sites must conform to certain accessibility principles. These can be grouped into the following main areas:

• use semantic markup that provides a meaningful structure to the document (i.e. Website page)
• Semantic markup also refers to semantically organizing the web page structure and publishing web services description accordingly so that they can be recognised 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 makes sense when read out of context. (e.g. avoid "Click Here.")
• don't use frames
• use CSS rather than HTML Tables for layout.
• author the page so that when the source code is read line-by-line by user agents (such as a screen readers) it remains intelligible. (Using tables for design will often result in information that is not.)

However, W3C permits an exception where tables for layout either make sense when linearized or an alternate version (that is perhaps linearized) is made available.

XHTML

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Since January 2000 all W3C Recommendations for HTML have been based on XML rather than SGML, using the abbreviation XHTML ('Extensible HyperText Markup Language). The language specification requires that XHTML Web documents must be "well-formed" XML documents – this allows for more rigorous and robust documents while using tags familiar from HTML.

One of the most noticeable differences between HTML and XHTML is the rule that all tags must be closed: 'empty' HTML tags such as <br> must either be 'closed' with a regular end-tag, or replaced by a special form: <br /> (note that there must be a space before the '/' on the end tag as otherwise the tag is not valid SGML). Another is that all attribute values in tags must be quoted.

CSS

Advantages of using CSS (Cascading Style Sheets) include:

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• Presentation information for an entire website or collection of pages can be held in one CSS file, allowing sweeping changes to be propagated with quick changes to this one file.
• Different users can have different style sheets: for example a large text alternative for visually-impaired users, or a layout optimized for small displays for mobile phones.
• The document code is reduced in size and complexity, since it does not need to contain any presentational markup.

Prior to CSS, nearly all of the presentational attributes of HTML documents were contained within the HTML markup; all font colours, 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 stylesheet resulting in considerably simpler HTML markup.