$(function() {
    var minHeight = $("#space").height();
    var idealHeight = $(window).height()-$("#content").outerHeight(true)-$("#about").outerHeight(true)-$("#menu").outerHeight(true);
    if(idealHeight > minHeight)
        $("#space").css("height", idealHeight);
    $(window).resize(function() {
        idealHeight = $(window).height()-$("#content").outerHeight(true)-$("#about").outerHeight(true)-$("#menu").outerHeight(true);
        if(idealHeight > minHeight)
            $("#space").css("height", idealHeight);
    });
});