document.getElementsByClassName = function (className) {
    var i, j, eltClass;
    var objAll = document.getElementsByTagName ? document.getElementsByTagName("*") : document.all;
    var objCN = new Array();
    for (i = 0; i < objAll.length; i++) {
        eltClass = objAll[i].className.split(/\s+/);
        for (j = 0; j < eltClass.length; j++) {
            if (eltClass[j] == className) {
                objCN.push(objAll[i]);
                break;
            }
        }
    }
    return objCN;
}

window.onload = function() {
    if(document.getElementById(cat)) {
        document.getElementById(cat).innerHTML = 'dummy';
    }
    var i;
    var len = document.getElementsByClassName("gog4s").length;
    for (i = 0; i < len; i++) {
        document.getElementsByClassName("gog4s")[i].style.display = "none";
    }
}