在页面中导入jquery.js和gobacktop.js就可以了，然后修改gobacktop.js中的图片路径，就可以使用了，一个不错的返回页面顶部的js,gobacktop.js是在网上找到的！

gobacktop.js的代码如下：

//** jQuery Scroll to Top Control script- (c) Dynamic Drive DHTML code library: http://www.dynamicdrive.com.
//** Available/ usage terms at http://www.dynamicdrive.com (March 30th, 09')
//** v1.1 (April 7th, 09'):
//** 1) Adds ability to scroll to an absolute position (from top of page) or specific element on the page instead.
//** 2) Fixes scroll animation not working in Opera. var scrolltotop={//startline: Integer. Number of pixels from top of doc scrollbar is scrolled before showing control//scrollto: Keyword (Integer, or "Scroll_to_Element_ID"). How far to scroll document up when control is clicked on (0=top).setting: {startline:1, scrollto: 0, scrollduration:1000, fadeduration:[500, 100]},controlHTML: '<img src="../images/top.png" style="width:39px; height:16px" />', //HTML for control, which is auto wrapped in DIV w/ ID="topcontrol"controlattrs: {offsetx:100, offsety:80}, //offset of control relative to right/ bottom of window corneranchorkeyword: '#top', //Enter href value of HTML anchors on the page that should also act as "Scroll Up" linksstate: {isvisible:false, shouldvisible:false},scrollup:function(){if (!this.cssfixedsupport) //if control is positioned using JavaScriptthis.$control.css({opacity:0}) //hide control immediately after clicking itvar dest=isNaN(this.setting.scrollto)? this.setting.scrollto : parseInt(this.setting.scrollto)if (typeof dest=="string" && jQuery('#'+dest).length==1) //check element set by string existsdest=jQuery('#'+dest).offset().topelsedest=0this.$body.animate({scrollTop: dest}, this.setting.scrollduration);},keepfixed:function(){var $window=jQuery(window)var controlx=$window.scrollLeft() + $window.width() - this.$control.width() - this.controlattrs.offsetxvar controly=$window.scrollTop() + $window.height() - this.$control.height() - this.controlattrs.offsetythis.$control.css({left:controlx+'px', top:controly+'px'})},togglecontrol:function(){var scrolltop=jQuery(window).scrollTop()if (!this.cssfixedsupport)this.keepfixed()this.state.shouldvisible=(scrolltop>=this.setting.startline)? true : falseif (this.state.shouldvisible && !this.state.isvisible){this.$control.stop().animate({opacity:1}, this.setting.fadeduration[0])this.state.isvisible=true}else if (this.state.shouldvisible==false && this.state.isvisible){this.$control.stop().animate({opacity:0}, this.setting.fadeduration[1])this.state.isvisible=false}},init:function(){jQuery(document).ready(function($){var mainobj=scrolltotopvar iebrws=document.allmainobj.cssfixedsupport=!iebrws || iebrws && document.compatMode=="CSS1Compat" && window.XMLHttpRequest //not IE or IE7+ browsers in standards modemainobj.$body=(window.opera)? (document.compatMode=="CSS1Compat"? $('html') : $('body')) : $('html,body')mainobj.$control=$('<div id="topcontrol">'+mainobj.controlHTML+'</div>').css({position:mainobj.cssfixedsupport? 'fixed' : 'absolute', bottom:mainobj.controlattrs.offsety, right:mainobj.controlattrs.offsetx, opacity:0, cursor:'pointer'}).attr({title:'Scroll Back to Top'}).click(function(){mainobj.scrollup(); return false}).appendTo('body')if (document.all && !window.XMLHttpRequest && mainobj.$control.text()!='') //loose check for IE6 and below, plus whether control contains any textmainobj.$control.css({width:mainobj.$control.width()}) //IE6- seems to require an explicit width on a DIV containing textmainobj.togglecontrol()$('a[href="' + mainobj.anchorkeyword +'"]').click(function(){mainobj.scrollup()return false})$(window).bind('scroll resize', function(e){mainobj.togglecontrol()})})}
}scrolltotop.init()

setting: {startline:1, scrollto: 0, scrollduration:1000, fadeduration:[500, 100]}, 

startline: 鼠标向下滚动了100px后出现#topcontrol*/

scrollto: 它的值可以是整数，也可以是一个id标记。若为整数（假设为n），则滑动到距离top的n像素处；若为id标记，则滑动到该id标记所在的同等高处

scrollduration:滑动的速度

fadeduration:#topcontrol这个div的淡入淡出速度，第一个参数为淡入速度，第二个参数为淡出速度

controlHTML: '',

controlHTML:控制向上滑动的，直接插入引动的图片，可以手动设置style。该处的html代码会被包含在一个id标记为#topcontrol的div中。

controlattrs: {offsetx:100, offsety:80}, 

controlattrs:控制#topcontrol这个div距离右下角的像素距离

anchorkeyword: '#top',

state: {isvisible:false, shouldvisible:false},

       state: isvisible:是否#topcontrol这个div为可见

               shouldvisible:是否#topcontrol这个div该出现