Auto resize image on webpage

function addOnloadEvent(fnc) {
    if (typeof window.addEventListener != "undefined")
        window.addEventListener("load", fnc, false);
    else if (typeof window.attachEvent != "undefined") {
        window.attachEvent("onload", fnc);
    }
    else {
        if (window.onload != null) {
            var oldOnload = window.onload;
            window.onload = function(e) {
                oldOnload(e);
                window[fnc]();
            };
        }
        else
            window.onload = fnc;
    }
}
function changeSize() {
    MAX_WIDTH=400;
    var imgs = document.getElementsByTagName("img");
    var l = imgs.length;
    for (i = 0; i < l; i++) {
        var img = imgs.item(i);
        cw = img.width;
        if (cw > MAX_WIDTH) {    
            img.width = MAX_WIDTH;
            img.height = img.height * MAX_WIDTH / cw;
        }
    }
}
addOnloadEvent(changeSize);