fearrr

var footer = $('.footer'),
    pageContainer = $('.page-container'),
    fixClass = 'navbar-fixed-bottom';

    function stickyFooter() {
        var windowHeight  = $(window).height(),
            contentHeight = pageContainer.height(),
            footerHeight  = footer.height();
        footer.removeClass(fixClass);
        if (contentHeight <= windowHeight-footerHeight){
            footer.addClass(fixClass);
        }
    }

    stickyFooter();
    $(window).resize(function () {
        stickyFooter();
    });

<div class="page-container">
    <section class="header"></section>
    <section class="nav"></section>
    <section class="content"></section>
</div>
<div class="footer">
</div>