var previewP;
function popup(file, w, h, scrll){
	var xleft = (window.screen.width/2)-(w/2);
	var xtop = (window.screen.height/2)-(h/2);
	if (previewP) previewP.close();
	previewP = window.open(file, 'popup1','left='+xleft+',top='+xtop+',width='+w+',height='+h+',status=0,scrollbars='+scrll);
	previewP.focus();
}