Avoid making the font size too small. Don't make frames and tables so wide that the viewer will have to scroll horizontally. Be selective about the number and types of fonts used. Avoid extensive use of all caps. To understand the web page content, viewers need to assimilate it into their own context.
Good graphics help the viewer interpret the content and move on to the next page.
Poor graphics force viewers to work for comprehension and to struggle to find the relationship between the content and their goals. Poor design attempts to fit too much onto one web page, applying innovation and creativity to squeezing in and contouring content. Speed Long waits are death to usability. Having a lot of downloaded graphics may result in a great web page but often means poor usability. I'm not aware of any studies on the length of time a person will spend waiting for a web page download to complete, but studies on response time show that people hate wait periods that take an indefinite amount of time.