CSS / Javascript如何在Firefox中做这个背景位置电影，就像它在IE7 +？
问题描述：
<script language="javascript" >
var speed=25; //speed
var num=0;
var photos = document.getElementById('head_image');
function scrollBG() {
num++;
photos.style.backgroundPosition="0"+num;
}
setInterval('scrollBG()',speed);
</script>
这是有问题的网站：www.theorymarine.com
This is the site in question: www.theorymarine.com
答
photos.style.backgroundPosition =0+ num;
photos.style.backgroundPosition="0"+num;
您需要一个CSS长度的单位。
You need a unit for CSS lengths.
photos.style.backgroundPosition= num+'px 0';
您可能还希望将动画放在时间上，开启速度或浏览器性能。例如：
You might also prefer to base your animation on the time, so that the rate it moves is not dependent on ‘speed’ or browser performance. eg.:
<script type="text/javascript">
var photos= document.getElementById('head_image');
var begin= new Date().getTime();
setInterval(function() {
var x= Math.floor((new Date().getTime()-begin)/25);
photos.style.backgroundPosition= x+'px 0';
}, 25);
</script>