大渝网招聘页面用到的 滚动后固定代码

<script>
$(document).ready(function(){
    var _width = ($(window).width() - 1003) / 2;
    var isIE6 = $.browser.msie && $.browser.version < 7 && !window.XMLHttpRequest;
    var obj = $('.list').get(0);
    $(window).scroll(function(){
        if((document.documentElement.scrollTop +document.body.scrollTop) >= 1049){
            if(!isIE6){
                $('.list').css({'position':'fixed','right':+_width+'px','top':0});
            }else{
                if (document.body.currentStyle.backgroundAttachment != "fixed") {
                    if (document.body.currentStyle.backgroundImage == "none") {
                        document.body.runtimeStyle.backgroundImage = "url(none.gif)"; // dummy
                        document.body.runtimeStyle.backgroundAttachment = "fixed";
                    }
                }
                obj.style.position = 'absolute';
                obj.style.setExpression("top", "eval((document.documentElement.scrollTop || document.body.scrollTop) - 590) + 'px'");
            }
        }else{
            $('.list').css({'position':'absolute','right':'0','top':'465px'});
        }
    });
});
</script>