back to top 回到顶部按钮 css+js

效果

html

<p id="back-to-top"><a href="#top"><span></span></a></p>

css

p#back-to-top{
      position:fixed;
      bottom:100px;
      right:80px;
}
p#back-to-top a{
      text-align:center;
      text-decoration:none;
      color:#d1d1d1;
      display:block;
      width:30px;
      /*使用CSS3中的transition属性给跳转链接中的文字添加渐变效果*/
      -moz-transition:color1s;
      -webkit-transition:color1s;
      -o-transition:color1s;
}
p#back-to-top a:hover{
      color:#979797;
}
p#back-to-top a span{
      background:#d1d1d1 url(../images/arrow_up.png) no-repeat center center;
      border-radius:6px;
      display:block;
      height:30px;
      width:30px;
      margin-bottom:5px;
      /*使用CSS3中的transition属性给<span>标签背景颜色添加渐变效果*/
      -moz-transition:background1s;
      -webkit-transition:background1s;
      -o-transition:background1s;
}
#back-to-top a:hover span{
      background:#979797 url(../images/arrow_up.png) no-repeat center center;
}

js

<script type="text/javascript">
$(document).ready(function(){
    //首先将#back-to-top隐藏
    $("#back-to-top").hide();
    //当滚动条的位置处于距顶部600像素以下时，跳转链接出现，否则消失
    $(function () {
        $(window).scroll(function(){
            if ($(window).scrollTop()>600){
                $("#back-to-top").fadeIn(500);
            }else{
                $("#back-to-top").fadeOut(500);
            }
    });
    //当点击跳转链接后，回到页面顶部位置
    $("#back-to-top").click(function(){
        $('body,html').animate({scrollTop:0},500);
            return false;
        });
    });
});
</script>