$(function(){
	$("img.rollover")
		.each(function(i) {
			var image_cache = new Object();
			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;
					}
				);
		}
		);
});