if(window.addEventListener) {
window.addEventListener("load", loadEvents, true);
}
else if(window.attachEvent) {
window.attachEvent("onload", loadEvents);
}

function loadEvents() {
var imgs = document.getElementsByTagName('img');
	for(var i = 0;i < imgs.length; i++) {
	var re = new RegExp('(^| )' + 'flip' + '( |$)');
		if(re.test(imgs[i].className)) {
		imgsrc = imgs[i].src;
		var newsrc = imgsrc.replace('2.jpg','1.jpg');
		var newimage = new Image();
		newimage.src = newsrc;
		imgs[i].onmouseover=changeImg;
		imgs[i].onmouseout=changeImgBack;
		}
	}
}

function changeImg() {
var isrc = this.src;
var newsrc = isrc.replace('1.jpg','2.jpg');
this.src = newsrc;
}

function changeImgBack() {
var isrc = this.src;
var newsrc = isrc.replace('2.jpg','1.jpg');
this.src = newsrc;
}