BrokenLinkCheck - Free Broken Link Checker / Online Dead Link Checking Tool - find bad hyperlinks
Coblis - If you are not suffering from a color vision deficiency it is very hard to imagine how it looks...
Dead Link Checker - Check for broken links on any website
Colour Blindness Simulator - Use our Colour Blindness Simulator to reveal how your images may appear to users with a variety of...
LinkChecker - LinkChecker is a free, GPL licensed website validator.
Colorblind Web Page Filter - Enter a URL, and this tool will render it as someone with color blindness will see it.