About eight percent of men are affected by some sort of color blindness. This is something to consider when developing the user interface of your site. There are several forms of color blindness but red-green blindness, is by far the most frequent form. Color Oracle is a free, system-level application that applies a filter to your screen to simulate the three most common types of red-green color-blindness.
One of the most critical components of a website affected by color blindness is the text link. Andy Rutledge has posted a great article on how to style your sites text links to make them more distinctive without having to resort to the hideous <blink> tag.