$(document).ready(function() {

  	$(".level_1").mouseover(function(){
  		$('img',this).attr("src","fileadmin/templates/images/link_arrow_over.gif");
  		}

  		).mouseout(function(){
  		
  		$('img',this).attr("src","fileadmin/templates/images/link_arrow.gif");
  		}
  		);
               });