$(document).ready(function(){
	   attachRollOverEvent(".menuImg");//list menu on top
  });

attachRollOverEvent = function(imageId){
	$(imageId).mouseover( function(){ $(this).attr("src", $(this).attr("src").split('_n').join('_o')) } );
	$(imageId).mouseout( function(){ $(this).attr("src", $(this).attr("src").split('_o').join('_n')) } );
}