Sorry I had to get off for a bit.. I see you found a way to do it.
I was going to give you this:
Code:
<script type="text/javascript">
// For each set of images, add these lines, incrementing each number at the end of the line for the pair.
image1 = new Image();
image1.src = "image_on.gif";
image2 = new Image();
image2.src = "image_off.gif";
</script>
<a href="html.html" onmouseover="document.scrollover1.src=image1.src" onmouseout="document.scrollover1.src=image2.src">
<img src="image_off.gif" name="scrollover1">
</a>