document.write('<div id="k_icopos" class="k_spico"><a href="javascript:void(0)" hidefocus="true" class="k_returntop bb" id="k_returntop" title="返回顶部"> </a></div><style>.k_spico {width:50px;height:50px;position:fixed;_position:absolute;display:none;cursor:pointer;}.k_returntop {display:block;width:50px;height:50px;background:url(http://csdnimg.cn/www/images/top_arrow.png) no-repeat 0 0;}.k_returntop:hover {filter:alpha(opacity=60);opacity:0.6;text-decoration:none;}</style>');
function addEvent(obj,type,fn){
if(!obj){return null;}
if(obj.addEventListener){
obj.addEventListener(type,function (ev){
var rtn=fn.call(obj,ev);
if(rtn==false){
ev.cancelBubble=true;
ev.preventDefault();
}
},false);
}else{
obj.attachEvent('on'+type,function (){
var rtn=fn.call(obj,event);
if(rtn==false){
event.cancelBubble=true;
return false;
}
})
}
};
function ReturnTop(obj,obj2,num,num2){
if(!obj){return null;}
this.obj = document.getElementById(obj);
this.obj2 = document.getElementById(obj2);
this.bSys = true;
this.scrollTop = 0;
this.timer = null;
this.iSpeed = 0;
this.iTop = 0;
this.iLeft = 0;
this.oBottom = num;
this.oWidth = num2;
var _this = this;
addEvent(window,'scroll',function(){
_this.moveFn();
})
addEvent(window,'resize',function(){
_this.moveFn();
})
}
ReturnTop.prototype.moveFn = function(){
var _this = this;
var GLOBAlIE6= /msie 6/ig.test(window.navigator.userAgent) && !/msie [1-57-9]/ig.test(window.navigator.userAgent);
this.scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
this.iTop = document.documentElement.clientHeight-this.oBottom+this.scrollTop;
this.iLeft = (document.documentElement.clientWidth-this.oWidth)/2+this.oWidth;
if(this.scrollTop>0){
this.obj.style.display = 'block';
this.obj.style.left = this.iLeft + 'px';
if(GLOBAlIE6){
this.obj.style.top = this.iTop + 'px';
if((css(document.body,'backgroundAttachment') !== "fixed") && (css(document.body,'backgroundImage') === "none")){
document.body.style.backgroundRepeat = "no-repeat";
document.body.style.backgroundImage = "url(about:blank)";
document.body.style.backgroundAttachment = "fixed";
}
}else {
this.obj.style.top = this.iTop-this.scrollTop + 'px';
}
}else {
this.obj.style.display = 'none';
}
if(!this.bSys){
clearInterval(_this.timer);
}
this.bSys = false;
this.obj2.onclick = function(){
_this.topFn();
_this.bSys = false;
}
}
ReturnTop.prototype.topFn = function(){
var _this = this;
clearInterval(_this.timer);
this.timer = setInterval(function(){
_this.setToFn();
},50)
}
ReturnTop.prototype.setToFn = function(){
var _this = this;
this.iSpeed = Math.floor(-this.scrollTop/8);
if(this.scrollTop==0){
clearInterval(_this.timer);
}
this.bSys = true;
document.documentElement.scrollTop = document.body.scrollTop = this.scrollTop + this.iSpeed;
}
var toTop = new ReturnTop('k_icopos','k_returntop',200,970);
