document.onclick= function(e) 
{
 var s= (e)?e.target:(event)?event.srcElement:"";
 if (s)
 { 
  var t= s.className.replace(/\boff\b/,"on");
  if (t===s.className) {t= s.className.replace(/\bon\b/,"off");}
  s.className= t;
 }
}