关于火狐节点不能插入的问题！

错误： uncaught exception: [Exception... "Node cannot be inserted at the specified point in the hierarchy" code: "3" nsresult: "0x80530003 (NS_ERROR_DOM_HIERARCHY_REQUEST_ERR)" location: "http://localhost:16861/WebSite/manager/ResourceLibrary/category.aspx Line: 70"]
有没有什么办法解决！

代码呢

JScript code

 function addCategory() {
            var lab = $get("#pctv");
            document.createElementPhotoCategory(lab);
        }

        document.createElementPhotoCategory = function (lab) {
            //li
            var newli = document.createElement("li");

            //输入框
            var input_text = document.createElement("input");
            input_text.type = "text";
            input_text.onfocus = function () {
                newli.className = "sli";
            }
            input_text.onblur = function () {
                newli.className = null;
            }

            newli.appendChild(input_text);
            lab.lastChild.appendChild(newli);
            input_text.focus();
        }

贴码贴出来了

自个解决了！