function popup(url,popup_width,popup_height,name) 
{
	popup_top = (screen.availHeight - popup_height) / 2;
	popup_left = (screen.availWidth - popup_width) / 2;
	window.open(url,name,"width="+popup_width+",height="+popup_height+",top="+popup_top+",left="+popup_left+",scrollbars=yes,menubar=no,status=no,resizable=no");
}