is cross browser compatible (IE6, IE7, Firefox, Opera, and Safari)
has separation of content and presentation (tableless CSS design only)
has markup elements used appropriately (such as tables for displaying data, correct use of radio buttons, checkboxes and other form elements, lists used appropriately, etc.)
uses as little markup as possible to get the job down (easier for readers and other assistive software)
makes sense with CSS turned off
makes sense with images turned off
allows the font size of the content to be manipulated by the end-user with no major disruption to the design of the site