<a href="#" 
onMouseOver="document.tanuki.src='graphics/tanuki_near.jpg'; status='Not a racoon, despite appearances'; return true;" 
onMouseOut="document.tanuki.src='graphics/tanuki_far.jpg'; status='';">
<img src="graphics/tanuki_far.jpg" alt="Tanuki" border=0 name="tanuki">
</a>

The critical bit here is that the image has been given a name ("tanuki"), which allows it to be addressed as a part of the document. This lets us change its source image (src) when the mouse rolls over it. The status (a property of window) is also changed. Multiple commands in the event handlers are separated by semicolons. The clause "return true" is necessary for changing window.status, although not, it would seem, for blanking it.

The use of "#" instead of a URL in the link anchor means that the user stays in the same page after clicking. We need to make this gadget an anchor rather than an isolated image, since the anchor tag allows us to play with events such as onMouseOver.