jQuery实现返回顶部

 1     /*返回顶部*/
 2     function toTop() {
 3         $(".to_top").hide();
 4         $(window).scroll(function(){
 5             var scroll_top = $(document).scrollTop();
 6             if(scroll_top != 0){
 7                 $(".to_top").show();
 8             }else{
 9                 $(".to_top").hide();
10             }
11         });
12         $(".to_top").click(function(){
13             $("body,html").animate({scrollTop:0},500);
14             $(".to_top").hide();
15            
16         });
17          $(".to_top").mouseover(function(){
18             $(".to_top").css({
19                 "filter":"alpha(opacity=70)",
20                 "-moz-opacity":"0.7",
21                 "opacity":"0.7"
22             });
23              return false;
24         });
25           $(".to_top").mouseout(function(){
26             $(".to_top").css({
27                 "filter":"alpha(opacity=50)",
28                 "-moz-opacity":"0.5",
29                 "opacity":"0.5"
30             });
31              return false;
32         });
33     }
34     toTop();

1 <div class="to_top" style="z-index:99999;display:block;">
2  </div> 

 1 /*这里是返回顶部按钮*/
 2 .to_top {
 3     position:fixed;
 4     display:block;
 5     background: url(../../images/footer-totop.png) no-repeat;
 6     filter:alpha(opacity=50);
 7     -moz-opacity:0.5;
 8     opacity:0.5;
 9     float:right;
10     width:60px;
11     height:60px;
12     margin-top:37%;
13     margin-left:95%;
14 }