Okay, this is a hard one.

I have a client who want a drop-down menu type thing only it is horizontal. For example you mouse-over a top menu item and a horizontal bar appears below with the sub-menu items that are part of the top menu item. Now thats fairly easy and it will degrade well because I will design it so that that menu will appear on the page belonging to the top menu item by default if javascript is not enabled. The hard part is that he wants it to animate when it opens. Because he doesn't want to use flash I was thinking I might be able to use an animated gif as a background to do all the dirty work of an animation. However, I'm not really sure how to pre-load the animation and get it to animate when the sub-menu is opened.

Can anyone help?