UPDATE: Now solved my problem by using an alternative method (see accepted answer for details).
Standard wordpress install, I have 4 navigation "buttons" along the bottom of the page. Each button consists of 2 animated gifs triggered by mouse-enter and mouse-out events. The idea is to have a puppet animal bounce up on hover, and then pop back down again when you move the mouse away (it's for a kids' nursery school)...
You can see what I'm trying for a limited time here:
Here's an example of the code I'm using:
<div id="foo">
<a href="mysite.com"
onMouseOver="document.images['tiger'].src='http://mysite.com/early/wp-content/themes/new/images/tigerup.gif'"
onMouseOut="document.images['tiger'].src='http://mysite.com/early/wp-content/themes/new/images/tigerdown.gif'"
onFocus="if(this.blur)this.blur()">
<img src="http://mysite.com/early/wp-content/themes/new/images/tigerdown.gif" name="tiger" border="0"> </a>
While it does work, it is not as reliable as I want. Sometimes the mouseover event fails to trigger the first gif animation, so any ideas to improve the effect would be much appreciated - thanks.