If you know what you want your mouse onClick event to be on, I'll assume it's on this button I'm going to demonstrate with --
<input type=button name=doIt value="Do It" onClick="startTheProcess();">
<script language=javascript>
function startTheProcess(){
//load the gif here
setTimeout('changeLocation();',3000);
}
function changeLocation(){
window.location='newPage.htm';
}
</script>
Sorry, I don't know the code to load up the gif image, but I'm sure someone else here can add to what I've posted. The setTimout will wait 3000 milliseconds and then fire the changeLocation() function, which will wisk you away to the 'newPage.htm' location...
you can change that 3000 to whatever you want...
good luck!

Paul Prewett