[RESOLVED] scrolling background

[merhaba]

hi,
I am tring to create a simple "scrolling background" but the result was a failure.
can you help me please,,
I have two images each is 999 pix of width ,the idea is when the first image is= to the left edge of the screen
I want the second image to follow the first one and so on...

<script>
var sstop=setInterval("run()",50)
function run()
{
var pic1 = document.getElementById("imagea");
 var pic2 = document.getElementById("imageb");
pic1.style.posLeft-=3;
if(pic1.style.posLeft<0)
{
pic2.style.posLeft=999;
pic2.style.posLeft-=3;
}
else
if(pic2.style.posLeft<0)
{
pic1.style.posLeft=999;
pic1.style.posLeft-=3;

}
}
</script>
<img src="aaa.gif" id=imagea style="position:absolute;left:1;width:999";>
<img src="bbb.gif" id=imageb style="position:absolute;left:999;width:999";>