function open_popup(url,name,_w,_h,_options)
{
   if (!_options) _options="toolbar=0,location=0,menubar=0,scrollbars=1,dependent=yes,alwaysRaised=1,directories=0,status=0,resizable=1";

    _left=(screen.width-_w)/2;
    _top=(screen.height-_h)/2;
                
    options="width="+_w+",height="+_h+",left="+_left+",top="+_top+","+_options;

    w=window.open(url,name,options);
    w.opener=self;	
    w.focus();

   return w;
}