$(document).ready(function(){
	$(".menu").hover(
  		function () {
    		$(this).css("backgroundImage","url(./image/category_bg_on.jpg)");
    		$("span",this).css("color","#fff");
		}, 
  		function () {
    		$(this).css("backgroundImage","url(./image/category_bg.jpg)");
			$("span",this).css("color","#36c");
		}
	);
	$("span").click(function(){
		$("++ul",this).animate(
			{ opacity  : "toggle" }
		);
	});
		var image_cache = new Object();
		$("img.rollover").not("[src*='_on.']").each(function(i) {
			var imgsrc = this.src;
			var dot = this.src.lastIndexOf('.');
			var imgsrc_on = this.src.substr(0, dot) + '_on' + this.src.substr(dot, 4);
			image_cache[this.src] = new Image();
			image_cache[this.src].src = imgsrc_on;
			$(this).hover(
				function() { this.src = imgsrc_on; },
				function() { this.src = imgsrc; }
			);	
		});

});