function popupform(myform, windowname, windowwidth, windowheight) {
	var winl_this = (screen.width - windowwidth) / 2;
	var wint_this = (screen.height - windowheight) / 2;
	if (! window.focus)return true;
	window.open('', windowname, 'height=' + windowheight + ',width=' + windowwidth + ',top=' + wint_this + ',left=' + winl_this + ',scrollbars=no');
	myform.target=windowname;
	return true;
}