Can anyone recommend a javascript where when the mouse is held over an image or link, a text box pops up with additional information? If you can submit a link so I can see it in action that would be great.

I'm reading CSS can do it also?

I've got this bookmarked – but I've never used it. I liked that it's just CSS, no additional JS required.
http://meyerweb.com/eric/css/edge/popups/demo.html

Scroll over the menu at left to see it work.

Tooltips at CodeCanyon

As requested.
http://progrower.coffeecup.com/picsmouseover.html

You are perfectly describing alternate text image labels

http://www.workhorsepainting.com/

on the link home pg the blue banner for the blog is a image and link and hover over the image you get the alternate text which describes the link I think it says "link to WHPC Blog"

That is what I was going to suggest. lol Because adding Javascript to do it for you is a bit much.

I think Amy is looking for tooltips not the alt attribute. Alt attributes are for screen readers and alternate text for missing images. Besides alt attributes don't pop up text boxes. Her inquiry regarding a JavaScript solution points to tooltips.

Fortunately for Amy, Eric's suggestion is super easy to use. My CodeCanyon link provides many other variations on the same principle at minimal cost for super functional, creative designs.