ページ下部のHTML5フッターの詳細（CSS＋JS）

<script type="text/javascript">
    $(function(){
        function footerPosition(){
            $("footer").removeClass("fixed-bottom");
                // Full text height of the page body
                var contentHeight = document.body.scrollHeight,
                //Visible window height, not including the top toolbar of the browser
                winHeight = window.innerHeight;
            if(! (contentHeight > winHeight)){
                //add class fixed-bottom for the footer when the page body height is less than the visible window height
                $("footer").addClass("fixed-bottom");
            } else {
                $("footer").removeClass("fixed-bottom");
            }
        }
        footerPosition();
        $(window).resize(footerPosition);
    });
</script>

.fixed-bottom {
    position: fixed;
    bottom: 0;
    width:100%;
}