function rollover(){
    if(document.getElementsByTagName){
        var images = document.getElementsByTagName("img");
        for(var i = 0; i < images.length; i++) {
            if(images[i].getAttribute("src").match("-2.")){
                images[i].onmouseover = function() {
                    this.setAttribute("src", this.getAttribute("src").replace("-2.", "-1."));
                }
                images[i].onmouseout = function() {
                    this.setAttribute("src", this.getAttribute("src").replace("-1.", "-2."));
                }
            }
        }
    }
}

if(window.addEventListener){
    window.addEventListener("load", rollover, false);
}else if(window.attachEvent){
    window.attachEvent("onload", rollover);
}