var thumbwindow = null;
function popup(mylink, windowname) {
   if (!window.focus) return true;
   var href;
   if (typeof(mylink) == 'string')
      href=mylink;
   else
      href=mylink.href;
   
   if (navigator.appName == "Microsoft Internet Explorer") {
      if ( !thumbwindow ) {
         thumbwindow = window.open(href, windowname, 
			           'width=550,height=420, scrollbars=yes');
      }
      else {
	     thumbwindow.close();
         thumbwindow = window.open(href, windowname,
					   'width=550,height=420, scrollbars=yes');
      }
   }
   else {
      if ( !thumbwindow || !thumbwindow.document ) {
         thumbwindow = window.open(href, windowname, 
					   'width=550,height=420, scrollbars=yes');
      }
      else {
    	 thumbwindow.close();
         thumbwindow = window.open(href, windowname, 
					   'width=550,height=420, scrollbars=yes');
      }
   }
   return false;
}