Old news but ...: Google, AOL, Yahoo improve service for the blind

W3C Web Content Accessibility Guideline 3. Use markup and style sheets and do so properly.
Mark up documents with the proper structural elements. Control presentation with style sheets rather than with presentation elements and attributes.
More: Web Content Accessibility Guidelines 1.0

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Appendix A. -- Validation
Validate accessibility with automatic tools and human review. Automated methods are generally rapid and convenient but cannot identify all accessibility issues. Human review can help ensure clarity of language and ease of navigation.
Begin using validation methods at the earliest stages of development. Accessibility issues identified early are easier to correct and avoid.
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2. Validate syntax (e.g., HTML, XML, etc.).
3. Validate style sheets (e.g., CSS).
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More: Web Content Accessibility Guidelines 1.0

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