Move multiple backgrounds infinitely using CSS

Question

I have two backgrounds:

body {
    background-image: url(img/nemo.png),url(img/ocean.png);
}

How do I make nemo.png background

Answer 1

This can be done with pure CSS 3, e.g keyframed animations:

Demo: http://jsfiddle.net/dghsV/112

body {
    background-image: url("http://www.animaatjes.nl/disney-plaatjes/disney-plaatjes/finding-nemo/nemo11.gif"), url("http://images2.layoutsparks.com/1/200022/ocean-dreams-blue-waves.jpg");
    background-repeat: no-repeat;
    background-position: 50% 0%, 0;
    -moz-animation: swim 2s linear 0s infinite;
    -webkit-animation: swim 2s linear 0s infinite;
    animation: swim 2s linear 0s infinite;
}
@-moz-keyframes swim {
    from { background-position: 200% 0, 0 0; }
    to  { background-position: -100% 0, 0 0; }
}
@-webkit-keyframes swim {
    from { background-position: 200% 0, 0 0; }
    to  { background-position: -100% 0, 0 0; }
}
@keyframes swim {
    from { background-position: 200% 0, 0 0; }
    to  { background-position: -100% 0, 0 0; }
}

Syntax

animation : animation-name animation-duration animation-timing-function animation-delay animation-iteration-count animation-direction;

The feature is experimental, so vendor-prefixes (eg -webkit-) have to be added (see also Can I use CSS3 Animation for compatibility notes). In my demo, I've used all properties, except for the last one.