Usability Examples
Typography
  Use boldface sparingly
  Avoid italics altogether
  Avoid using all caps
  Use sans-serif fonts
  Avoid underlining

Miscellaneous
  Avoid horizontal scrolling
  Avoid animation
 Alignment
  Left justify text
  Avoid double spacing
  Top align text

Color
  Use light backround colors
  Avoid using different font colors

Avoid horizontal scrolling
Stay within a 760-pixel width and users will not have to scroll horizontally. To avoid horizontal scrolling, set table widths less than 100%.

Information was taken from "Building Effective Web Sites" by Dr. Frost and Judy Strauss