帮忙写个菜单

<body>
<input type=button value=popmenu onclick=divstyle()>
<br>
<img id=selimg height=30 width=40 src=http://www.csdn.net/expert/images/rank/user2.gif onclick=showsel() style="display:none">
<select name=mysel style="visibility:visible">
<option value="1">1</option>
<option>2</option>
<option>2</option>
<option>2</option>
<option>2</option>
<option>2</option>
</select>
<div id=menu style="visibility:hidden;background:green;left: 10; top: 48; width: 400; height: 80; position: absolute; z-index: 1" >menu</div>
</body>
<script>
i=0;
function divstyle()
{
if(Math.round(i/2)==(i/2))
{
menu.style.visibility='visible';
document.all.mysel.style.visibility='hidden';
document.all.selimg.style.display='block';
}
else
{
menu.style.visibility='hidden';
document.all.mysel.style.visibility='visible';
document.all.selimg.style.display='none';
}
i++;
}
function showsel()
{
document.all.mysel.style.visibility='visible';
document.all.selimg.style.display='none';
}
</script>