I'd also like to point out that using the TITLE tag to popup descriptions of objects (a tool tip) complies with the latest W3C Accessibility Guidelines. Using ALT tags for this purpose does not. In fact, the use of the ALT has changed somewhat. However, people are still using it.

Another solution is to use layers. Have a layer with some copy (a description) in it pop up when you move your mouse over the object. But, you will need to know JS and HTML fairly well to do this.