function popup_url(url, size_w, size_h, scroll) {
	new_size_w = Number(size_w)+10;
	new_size_h = Number(size_h)+25;
	popup_left = Math.round((screen.availWidth-new_size_w)/2);
	popup_top = Math.round((screen.availHeight-new_size_h)/2);
	msg=open(url,"POPUP","scrollbars="+scroll+",toolbar=no,directories=no,width="+size_w+",height="+size_h+",menubar=no, top="+popup_top+", left="+popup_left+"");
	msg.document.close();
	msg.focus();
};