window.onload=function(){
	$$('table.tab tbody tr').each(  
     function(e) {   
       Event.observe(e, "mouseover", function(e){ Event.findElement(e,'tr').addClassName('highlight_row');});  
       Event.observe(e, "mouseout", function(e){ Event.findElement(e,'tr').removeClassName('highlight_row');}); 
     }  
   ); 
	
}