Compared to text, they take a long time to download and render, causing users with slow modems and old computers to gnash their teeth. I can think of four good reasons and a few bad reasons. Good Reasons Illustration. When an image illustrates the text or is itself the information conveyed, that's a fine reason to use an image. One good example is a map, like room 343 in Altgeld Hall .
Graphics can be useful to help people find their place in three ways.
First, if a Web page is long enough that readers have to scroll, graphic elements can help readers keep track of where on the page they are. Second, if there are multiple areas on a Web site, an image can help readers remember on what page they saw something or even what area of the Web site they were in. Third, if a navigation bar is graphic, that can help readers quickly find the navigation bar on the page. Consistent use of graphics can help to unify a site. This makes it easier for readers to tell when they have left your site and moved to someone else's.