function showModal() {
    var mpop = $('#backgroundPopup');
    mpop.css({ "opacity": "0.7" });
    mpop.fadeIn("slow");

    var windowWidth = document.documentElement.clientWidth;
    var windowHeight = document.documentElement.clientHeight;
    var popupHeight = $("#content").height();
    var popupWidth = $("#content").width();
    //centering
    $("#content").css({
        "top": windowHeight / 2 - popupHeight / 2,
        "left": windowWidth / 2 - popupWidth / 2
    });
    $('#content').fadeIn("fast");
};
function closePopup() {
    $('#backgroundPopup, #content').fadeOut("fast");
};