IE6 扫描页面 select 并用iframe 遮挡

$.fn.fix_ie6Select = function () { 
        /// <summary> 
        /// 兼容弹出层在 IE6 下不能掩盖 Select 
        /// </summary> 
        return this.each(function (index) { 
            var frm = $(this).find('iframe[tag*="ie6Selector"]'); 
            if ($.browser.version == "6.0") { 
                var w = $(this).width(); 
                var h = $(this).height(); 
                if (frm.length == 0) { 
                    $(this).prepend('<iframe tag="ie6Selector" src="" frameborder="no" marginwidth="0" marginheight="0" style="border:none;position:absolute;visibility:inherit;top:0px;left:0px;width:' + w + 'px;height:' + h + 'px;z-index:-1;"></iframe>'); 
                }  
                else { 
                    frm.css("width", w); 
                    frm.css("height", h); 
                } 
            } 
        }); 
    };