High on the list of usability¹ issues it the ability to be able to read the site. One of the biggest impediments to easy reading is contrast between the letters on the page and background.

For example, here is a really classy looking site, Everson Museum of Art.

Notice the black-on-gray letters in the left column. Many people, including me, find this a difficult read. Readibility is worsened further by too-tiny type.

Fortunately, there is an objective test to assist designers with contrast issues, AccessKeys.

Thanks to Web Pages that Suck for this tip.