//-------------値設定---------------

var tagN = "img";	//タグ名を指定
var classN = "ymt-crd-btn";	//クラス名を指定
var overN = "_ov";	//マウスオーバー時の画像ファイル名
var TempSrc;
//---------------------------------


function chgimg_over(myImgURL){
	TempSrc = myImgURL.getAttribute('src');
	myImgURL.setAttribute('src', myImgURL.getAttribute('ovsrc'));
}

function chgimg_out(myImgURL){
	if (!TempSrc) TempSrc = myImgURL.getAttribute('src');
	myImgURL.setAttribute('src', TempSrc);
}

function mouseEvent() {
	if (!document.getElementsByTagName) return false;
	
	var preLoad = new Array();
	var links = document.getElementsByTagName(tagN);
	
	for (var i=0; i < links.length; i++) {
		if (links[i].className.match(classN)) {

			var src = links[i].getAttribute('src');
			var ftype = src.substring(src.lastIndexOf('.'), src.length);
			var ovsrc = src.replace(ftype, overN +ftype);

			links[i].setAttribute('ovsrc', ovsrc);
			preLoad[i] = new Image();
			preLoad[i].src = ovsrc;

			links[i].onmouseover = function() {	chgimg_over(this);}
			links[i].onmouseout = function() {	chgimg_out(this);}

		}
	}
}

try{
	window.addEventListener("load",mouseEvent,false);
}catch(e){
	window.attachEvent("onload",mouseEvent);
}