new function(){
	//p = console.log;
	//window.onload = function(){
	function rollover(){
		var conf = {
			className : 'btn',
			postfix : '_hover'
		};
		var imgNodeList = getElementsByClassName(conf.className);
		var node;
		for (var i=0, len=imgNodeList.length; i<len; i++) {
			node = imgNodeList[i];
			node.originalSrc = node.src;
			node.rolloverSrc = node.originalSrc.replace(/(\.gif|\.jpg|\.png)/, conf.postfix+"$1");
			preloadImage(node.rolloverSrc);
			node.onmouseover = function(){
				this.src = this.rolloverSrc;
			};
			node.onmouseout = function(){
				this.src = this.originalSrc;
			};
		}
	};
	//クラス名によるエレメントノード配列取得
	function getElementsByClassName(name){
		var elements = [];
		var allElements = document.getElementsByTagName('*');
		for (var i=0, len=allElements.length; i<len; i++) {
			if (allElements[i].className == name){
				elements.push(allElements[i]);
			}
		}
		return elements;
	}
	//プリロード
	preloadedImages = [];
	function preloadImage(url){
		var p = preloadedImages;
		var l = p.length;
		p[l] = new Image();
		p[l].src = url;
	}

	function addEvent(elm,listener,fn){
		try{
			elm.addEventListener(listener,fn,false);
		}catch(e){
			elm.attachEvent("on"+listener,fn);
		}
	}
	addEvent(window,"load",rollover);
}