Web Accessibility

It is very important to respect web accessibility guidelines, to make a website accessible to people with disabilities or who are using for any reason a web browser with limited capabilities. Accessibility guidelines help also in designing a valid HTML/CSS and search engine friendly website.

Text Size -
Web Content Accessibility Guidelines -
Verification Tools -
Reference Links

There are specialized interfaces for text conversion to speech or Braille, but something quite easy to do is resizing text on a web browser, for example by using the View option of the browser menu: View >Text Size or View > Increase Font. Some browsers do not resize text in this way if the font size has been specified in the HTML or stylesheets code, so it is preferable to use relative font size units instead of absolute units.

Web Content Accessibility Guidelines

W3C Web Content Accessibility Guidelines 1.0 explains how to achieve better web design for people with disabilities or that are browsing the web under some constraints (mobile phone, noisy or hand-free environment, text browsers like Lynx, etc.) Some examples:

Colours that are necessary to the document should be explained in text. Unecessary colour information should be given in style sheets, so that the user can change it if necessary with their own style sheets.
It is a good idea to have contrasting background and foreground colours, especially for text.
Images important to the content should be described in text, using the longdesc img attribute. All images should have a short description or title with the alt attribute (this is also a HTML/XHTML validation requirement).
Animation should be achieved at a good speed (not too fast, not too slow) and it should be possible to stop or pause.
Icons and images can be useful for people with cognitive or learning disabilities, etc.
Table structure (head, body) should be defined and summary of tables should be provided where necessary.
It is a good idea to provide alternatives to the use of event handlers such that a mouse.
It is preferable not to open pop-up windows, and if doing so, to clearly announce this in advance.
About links in a page - the anchor text for a link should be relevant to the content of its URL, there should be some text separating successive links (unless the links are items like <li> in a list), the same text should not be used as anchor text for links to different URLs.

Verification Tools

webxact.watchfire.com/: Watchfire WEBXACT
wave.webaim.org/: WAVE 3.0
www.contentquality.com/: HiSoftware Cynthia Says Portal

Reference Links

www.w3.org/WAI/: W3C Web Accessibility Initiative
www.w3.org/TR/WAI-WEBCONTENT/: W3C Web Content Accessibility Guidelines 1.0
www.w3.org/TR/xmlgl: W3C XML Accessibility Guidelines
www.w3.org/QA/Tips/font-size: Care With Font Size - W3C Quality Tips for Webmasters
www.rnib.org.uk/xpedio/groups/public/documents/publicwebsite/public_goodwebdesign.hcsp: RNIB's page on good Web Design
www.webaim.org/: WebAIM Web Accessibility Information and Solutions
www.macromedia.com/macromedia/accessibility/: Macromedia - Accessibility
www.bda-dyslexia.org.uk/: The British Dyslexia Association
www.lighthouse.org/color_contrast.htm: Effective Color Contrast - Designing for for People with Partial Sight and Color Deficiencies, Lighthouse International
diveintoaccessibility.org/: Dive Into Accessibility