<input type="button" value="隐藏内容" onclick = "hidden()">

    <input type="button" value="显示内容" onclick = "show()">

    <input type="button" value="取消设置" onclick = "unSetting()">

  </form>

  <script type="text/javascript">

//定义"改变颜色"的函数

    function changeColor(){

        var mychar = document.getElementById("txt");

        mychar.style.color = "red";

        mychar.style.backgroundColor = "#ccc";

    }

//定义"改变宽高"的函数

    function changewihe(){

        var mychar = document.getElementById("txt");

        mychar.style.width = "500px";

        mychar.style.height = "600px";

    }

//定义"隐藏内容"的函数

    function hidden(){

       var mychar = document.getElementById("txt");

       mychar.style.display = "none";

    }

//定义"显示内容"的函数

    function show(){

     document.getElementById("txt").style.display = "block";

    }