Button Lên Trên - Xuống dưới ẩn hiện với hiệu ứng trượt nhẹ nhàng

Thêm CSS

#gotop{cursor:pointer;width:30px;height:30px;position:fixed !important;position:absolute;z-index:999;text-indent:-9999px;border:1px solid #144F69;background-color:#067BAF;background-image:-webkit-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:-moz-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:-ms-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:-o-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:radial-gradient(ellipse at center top,#2493C4,#086A95);-webkit-box-shadow:inset 0 0 0 1px #2493C4,0 1px 3px black;-moz-box-shadow:inset 0 0 0 1px #2493C4,0 1px 3px black;box-shadow:inset 0 0 0 1px #2493C4,0 1px 3px black;-webkit-border-radius:10px 0 0 0;-moz-border-radius:10px 0 0 0;border-radius:10px 0 0 0;overflow:hidden}
#gotop:hover:after{border-bottom-color:white}
#gotop:after{content:"";display:block;width:0;height:0;border-width:10px 4px;border-style:solid;border-color:transparent transparent #C3D1D7 transparent;position:absolute;top:0;left:11px}
#gobottom{cursor:pointer;width:30px;height:30px;position:fixed!important;position:absolute;top:26px;right:0;z-index:99;text-indent:-9999px;border:1px solid #144F69;background-color:#067BAF;background-image:-webkit-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:-moz-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:-ms-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:-o-radial-gradient(ellipse at center top,#2493C4,#086A95);background-image:radial-gradient(ellipse at center top,#2493C4,#086A95);-webkit-box-shadow:inset 0 0 0 1px #2493C4,0 1px 3px black;-moz-box-shadow:inset 0 0 0 1px #2493C4,0 1px 3px black;box-shadow:inset 0 0 0 1px #2493C4,0 1px 3px black;-webkit-border-radius:0 0 0 10px;-moz-border-radius:0 0 0 10px;border-radius:0 0 0 10px;overflow:hidden}
#gobottom:hover:after{border-top-color:white}
#gobottom:after{content:"";display:block;width:0;height:0;border-width:10px 4px;border-style:solid;border-color:#C3D1D7 transparent transparent transparent;position:absolute;top:10px;left:11px}

Javascript

<script type='text/javascript'>
//<![CDATA[
$(window).scroll(function () {
    if ($(this).scrollTop() > 100) {
        $("#gotop").removeAttr("href");
        $("#gotop").stop().animate({
            bottom: "0",
            right: "0"
        }, {
            duration: 800,
            queue: false
        })
    } else {
        $("#gotop").stop().animate({
            bottom: "-50",
            right: "-50"
        }, {
            duration: 1000,
            queue: false
        })
    }
   if ($(this).scrollTop() > 100) {
        $("#gobottom").removeAttr("href");
        $("#gobottom").stop().animate({
            top: "-50",
            right: "-50"
        }, {
            duration: 800,
            queue: false
        })
    } else {
        $("#gobottom").stop().animate({
            top: "0",
            right: "0"
        }, {
            duration: 1000,
            queue: false
        })
    }

});
$(function () {
    $("#gotop").click(function () {
        $("html, body").animate({
            scrollTop: 0
        }, "slow");
        return false
    })
    $("#gobottom").click(function () {
        $("html, body").animate({
            scrollTop: $('#footer').offset().top
        }, 970);
        return false
    })
});
//]]>
</script>
<a id="gotop" style="bottom: -50px; right: -50px;">Lên Trên!</a>
<a id="gobottom" style="top: 0px; right: 0px;">Xuống Dưới!</a>
<div id='footer'/>