Saw a great article on .Net magazines site on how to create a 404 page with CSS 3 animation for browsers that support it. At the moment both Firefox 5 and Chrome support CSS3 animation (works on iPhone/iPad too), this will be great workaround for flash for simple banner ads. No more resorting to animated gifs.
So I had to make my own 404 page with the animation implemented. Check it out here. (Please note this was for the old theme).
At the moment it can only be implemented with vendor prefixed properties. Setting an animation name and setting a key frame. For a great guide on how to do it all check out the article on .Net magazine.