js实现网页页面回到顶部

<script language="javascript">
$(function(){
    var $backToTopTxt = "返回顶部", $backToTopEle = $('<div class="backToTop"></div>').appendTo($("body"))
    .text($backToTopTxt).attr("title", $backToTopTxt).click(function() {
    $("html, body").animate({ scrollTop: 0 }, 120);
}), $backToTopFun = function() {
    var st = $(document).scrollTop(), winh = $(window).height();
    (st > 0)? $backToTopEle.show(): $backToTopEle.hide();
    //IE6下的定位
    if (!window.XMLHttpRequest) {
    $backToTopEle.css("top", st + winh - 166);
    }
};
$(window).bind("scroll", $backToTopFun);
$(function() { $backToTopFun(); });
});
</script>

css样式，完成在页面右下边栏竖向显示“返回顶部”4个字

<style>
/*返回顶部*/
.backToTop {display: none; width: 18px; line-height: 1.2; padding: 5px 0; background-color: #000; color: #fff; font-size: 12px; text-align: center; position: fixed; _position: absolute; right: 10px; bottom: 100px; _bottom: "auto"; cursor: pointer; opacity: .6; filter: Alpha(opacity=60);}
</style>