我有段让背景移动的代码。可是它只是横着移。我想让他向下移动要 怎么改
1<script language="JavaScript">
2var backgroundOffset=0;
3var bgObject=eval('document.body');
4function scrollBG(maxSize){
5backgroundOffset=backgroundOffset+1;
6if(backgroundOffset>maxSize)backgroundOffset=0;
7bgObject.style.backgroundPosition="0"+backgroundOffset;
8}
9var ScrollTimer=window.setInterval("scrollBG(307)",64);
10</script>
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1<script language="JavaScript">
2var backgroundOffset=0;
3function scrollBG(maxSize){
4backgroundOffset=backgroundOffset+1;
5if(backgroundOffset>maxSize)backgroundOffset=0;
6document.body.style.backgroundPositionY="0"+backgroundOffset;
7}
8var ScrollTimer=window.setInterval("scrollBG(307)",64);
9</script>