Rp Tutorials

So, I'm not sure if I'll be able to word this right, but... Does anyone know how to make images in your layout header slide down when you hover over it? I saw a journal awhile back, but I can't remember what it was to show as an example. It would be similar to this, but the image on the right would move down when you moused over. I know it's CSS3, but no matter what I try nothing seems to work.