function inputRollover() {
    if(document.getElementsByTagName) {
        var inputs = document.getElementsByTagName("input");
        for(var i=0; i < inputs.length; i++) {
            if(inputs[i].getAttribute("src").match("_off.")) {
                inputs[i].onmouseover = function() {
                    this.setAttribute("src", this.getAttribute("src").replace("_off.", "_on."));
                }
                inputs[i].onmouseout = function() {
                    this.setAttribute("src", this.getAttribute("src").replace("_on.", "_off."));
                }
            }
        }
    }
}

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