function switch_img(obj)
{
if (obj)
   {
   if (obj.src)
         {
			numimg = obj.src.substr(obj.src.lastIndexOf('.')-1, 5);
			nomimg = obj.src.substr (obj.src.lastIndexOf('/')+1, obj.src.length-6 - obj.src.lastIndexOf('/'));
			if (numimg == "1.gif" ) {
 				obj.src = "_images/menu/" + nomimg + "2.gif";
 			}
 			else {
 				obj.src = "_images/menu/" + nomimg + "1.gif";
 			}
 			
          }
   }
}