Oh, I write my pages in a text editor as well. But I write my CSS using a CSS editor that provides styled selector listing, auto-completion and indenting as well as a GUI panel for making parameter changes/edits without having to write the CSS by hand.

I must have missed the fact that the content displays properly if not a mov. Interesting. You might also try relative positioning. It will be relative to the containing block, so you'll have to adjust the offset.

With regards to the corners... Neither of my suggestions should make animating any more difficult. In the first instance each image would have the corner built-in. So no change to any animation or page code. In the second, you would set the Z position of the corners higher than the animated content. That's an easy way to make them always appear over top. Make sure to set position relative on the elements.