function popitup(url) {
if ($_newwindow && !$_newwindow.closed && $_newwindow.location) {
    $_newwindow.location.href = url; 
    $_newwindow.focus(); } 
else { 
       width = 800, height = 600; 
       x = (640 - width)/2, y = (480 - height)/2;

        if (screen) {
             y = (screen.availHeight - height)/2;
             x = (screen.availWidth - width)/2;
        }		

	$_newwindow=window.open(url,'htmlname','width=800,height=600,resizable=no');
	$_newwindow.moveTo(x,y);
} 
}


function tidy() {
   if ($_newwindow && !$_newwindow.closed && $_newwindow.location) { 
		$_newwindow.close(); 
   } 
}