if ($('productDescription').offsetHeight > 320) {
    var mooDescription = new fx.HeightMin('productDescription');
    mooDescription.toggle();

    function mooDescriptionClick() {
        mooDescription.toggle();
    }

    var elP;
    var elA;
    elP = document.createElement("p");
    elA = document.createElement("a");
    elA.href = "#";
    if (elA.addEventListener) {
        elA.addEventListener("click", mooDescriptionClick, false);
    } else {
        elA.onclick = mooDescriptionClick;
    }
    elA.appendChild(document.createTextNode("Click here to show/hide the full description"));
    elP.appendChild(elA);
    $("prod_details").appendChild(elP);
}