Add a short CSS class to an HTML Web page to use animated and stationary GIF images as the page's background.

CSS 3 has some awesome new animation capabilities for web developers — rotating objects, fading them in and out and more — but writing the code is a bit more complicated than most CSS rules ...

One way to add a background photo to any custom Tumblr theme is to embed a simple CSS tag at the right location in the theme's HTML code.