Validation Tools
Handy tools for Automated Validation
Disclaimer: While automated validation tools are useful in identifying website accessibility flaws, they do not and should not be used as an only-alternative to manual human validation testing.
CSS
To validate cascading style sheets, visit: http://jigsaw.w3.org/css-validator/
XHTML
To validate XHTML code, visit: http://validator.w3.org/
Accessibility
Test compliance with the 508 Standards and WCAG Guidelines:
Watchfire (formerly, "Bobby")
This automated accessibility checker is one of the most popular among web masters. Visit: http://webxact.watchfire.com/.
Cynthia Says
Another handy automated accessibility checker. Visit: http://www.cynthiasays.com.
ColorBlind Web Page Filter
Test how your website's accessibility to people with color-blindness. Visit: http://colorfilter.wickline.org/.
Juicy Studio Color Contrast Analyzer
Another tool for testing color and contrast. Visit: http://juicystudio.com/services/colourcontrast.php