var  uploadImgSizeLimit=function(target){
        alert(target);
            //以下校驗圖片大小
            var agent = window.navigator.userAgent;
            var isIE=/msie/i.test(agent) && !window.opera;
            var fileSize = 0;
            if (isIE && !target.files) {
             //如果是ie6以下的版本，直接fileSize可以獲取到大小
                if (agent.indexOf("MSIE 5.0") > 0 || agent.indexOf("MSIE 6.0") > 0) {
                    var img = new Image();
                    var fname = target.value;
                    img.src = fname;
                    fileSize = img.fileSize;
                }else {
                    //ie7版本以上需要打開安全設置
                     try {
                           var fso, f, fname, fsize;
                            var flength = 1000; //設置上傳的文件最大值（單位：kb），超過此值則不上傳。
                            var finame = target.value;
                            fso = new ActiveXObject("Scripting.FileSystemObject");
                            f = fso.GetFile(finame);//文件的物理路徑
                            fname = fso.GetFileName(finame);//文件名（包括擴展名）
                            fileSize = f.Size; //文件大小（bit）
                        }

                     catch(e){
                                alert(e "\n 跳出此消息框，是由于你的activex控件沒有設置好,\n"
                                 "你可以在瀏覽器菜單欄上依次選擇\n"
                                 "工具->internet選項->\"安全\"選項卡->自定義級別,\n"
                                 "打開\"安全設置\"對話框，把\"對沒有標記為安全的\n"
                                "ActiveX控件進行初始化和腳本運行\"，改為\"啟動\"即可");
                            return false;
                     }
                }
            }else {
        //    火狐版本下的文件大小獲取
                fileSize = target.files[0].size;
            }  
             var size = fileSize / 1024;
             alert(size);
        
        
        
             return false;
        };