给moz-firefox下添加IE方法和属性

    Node.children                yes        yes            no            no                    no
    Node.hasChildNodes            yes        yes            yes            yes                    no
    Node.childNodes                yes        yes            yes            yes                    no
    Node.swapNode                yes        no            no            no                    no
    Node.currentStyle            yes        yes            no            no                    no

    */
    Node.prototype.replaceNode=function(Node){// 替换指定节点
        this.parentNode.replaceChild(Node,this);
        }
    Node.prototype.removeNode=function(removeChildren){// 删除指定节点
        if(removeChildren)
            return this.parentNode.removeChild(this);
        else{
            var range=document.createRange();
            range.selectNodeContents(this);