Hello Guys

I am using a javascript function to open the window.The window is opening
correctly in IE 7,Firefox.But it is not opening in IE 6.
The code I have used is

Code JavaScript:
function OpenPopUp(imageid)
	var iWidth=820;
	var iHeight=620;
	var myURL="imagepopup.php?image_id="+imageid;
	posLeft = (screen.width - iWidth)/2;
        posTop = (screen.height - iHeight)/2; 	            window.open(myURL,"_blank","toolbar=no,location=yes,directories=no,status=yes,menubar=no,scrollbars=yes,resizable=yes,width=820,height=620,left="+posLeft+",top="+posTop);

Please help me out.Its urgent.
The html code I used is
HTML Code:
<a href="#" onclick="javascript:OpenPopUp(<?=$imgAid?>);">Open Image</a>
Your help will be highly appriciated.