$(document).ready(function() {
 $("#nav img").mouseover( function() {	
	var title=$(this).attr("src");
	var roll=title.replace( "[1].gif","[2].gif")
	$(this).attr("src",roll);
   } );
 $("#nav img").mouseout( function() {	
	var title=$(this).attr("src");
	var roll=title.replace( "[2].gif","[1].gif")
	$(this).attr("src",roll);
   } );
});