function getElement(id) {
    if (document.all)
        return document.all[id];
    else if (document.getElementById)
        return document.getElementById(id);
}

function hideObject(id) {
    getElement(id).style.display = "none";
}

function showObject(id) {
    getElement(id).style.display = "block";
}

function centerElementXY(id) {
    var element = getElement(id);
    objh = parseFloat(element.clientHeight) / 2;
    objw = parseFloat(element.clientWidth) / 2;
    element.style.top  = Math.floor(Math.round((document.documentElement.offsetHeight / 2) + document.body.scrollTop) - objh) + 'px';
    element.style.left = Math.floor(Math.round((document.documentElement.offsetWidth / 2) + document.body.scrollLeft) - objw) + 'px';
}