jquery 支持ie6下position为fixed的方法

<!--[if lte IE 7]>

<script type="text/javascript">

(function($) { 

    $.fn.pozFixed = function(params) { 

        var defaults = { 

            top : 400, 

            left : '50%',

            interval:100

        }; 

        defaults = $.extend(defaults,params);     

        return this.each(function(i,o) { 

            var $this = $(this); 

            this.fixPosition = function() { 

            var st = $().scrollTop();  

                $this.css({

                    top:st + defaults.top,

                    left:'50%'

                });               

            };

            $this.css({position:'absolute',top:defaults.top,left:"50%"}); 

            setInterval(this.fixPosition,defaults.interval); 

        });

    };

})(jQuery);

</script>

<![endif]-->

http://be-evil.org/post-116.html