$(document).ready(function() {
    setTopMargin($("#page"));
});
// --- calculates top margin - to make page vertically centered ---
// --- supplied value is body (man div element) to be centered ---
function setTopMargin(body)
{
    // page - body element
    // this was before when size of the content was static
    //var margin = $(document).height() - $("#page").height();
    var margin = $(document).height() - 600;

    // check if margin is not negative
    if (margin > 0) {
        margin = margin / 2;
    } else {
        margin = 0;
    }

    // set margin top
    $(body).css("margin-top", margin + "px");
}