//画像のロールオーバー
$(function(){
			var conf = {
			className : 'btn',
			postfix : '_on'
			};
			$('.'+conf.className).each(function(){
						this.originalSrc = this.src;
						this.rolloverSrc = this.originalSrc.replace(/(\.gif|\.jpg|\.png)/, conf.postfix+"$1");
						preloadImage(this.rolloverSrc);
			}).hover(function(){
						this.src = this.rolloverSrc;
			},function(){
						this.src = this.originalSrc;
			});
});

//ロールオーバー向け画像プリロード
preloadImages = [];
			function preloadImage(url){
			var p = preloadImages;
			var l = p.length;
			p[l] = new Image();
			p[l].src = url;
}