<disclaimer>Okay, I know nothing of javascript yet.</disclaimer>

I want to make a simple onmouseover for some images that will bring up a tool tip box with text. I'm working at the moment through a "dummy editor" provided by a webhosting company and I do not have access to edit the header section of this site. Help!

use the title attribute for the <img> tag

<img src="image-path" alt="Alternate Text" title="This text will appear on MouseOver">

It is actually used for accessibility devices so it serves a dual purpose.