New Accessibility Guidelines Part IV: Robustness
http://www.practicalecommerce.com/articles/1114-New-Accessibility-Guidelines-Part-IV-Robustness

Dolson, Joseph C.
Practical eCommerce
2009

Abstract:

The fourth principle of the Web Content Accessibility Guidelines requires new web documents to be “robust.” Robustness, future-proofing, user-agent independence, accessibility-supported: All are terms that suggest the same basic idea that your documents should follow standard, supported models for web document types. In many ways, this is the simplest and most testable requirement of the WCAG, but the details can be quite complicated.