JavaScript如何使页面慢慢向上运行？

如何使页面慢慢向上运行？
<SCRIPT LANGUAGE="JAVASCRIPT">
<!--
var position = 0;
var timeoutid=null;
function scrollhtml() {
if (position < 400 ){
position++;
scroll(0,position);
clearTimeout(timeoutid);
timeoutid = setTimeout("scrollhtml()",100); }
else{
clearTimeout(timeoutid);
scroll(0,0);
}}
-->
</SCRIPT>

<input type="button" name="submit" value="开始滚动" onClick="scrollhtml()">