                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript入门篇

有人能帮忙看下为什么我的代码运行不起来吗?多谢了！

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" Content="text/html; charset=utf-8" />
<title>javascript</title>
<style type="text/css">
body{font-size:12px;}
#txt{
    height:400px;
    width:600px;
   border:#333 solid 1px;
   padding:5px;}
p{
   line-height:18px;
   text-indent:2em;}
</style>
</head>
<body>
<h2 id="con">JavaScript课程</H2>
<div id="txt">
     <h5>JavaScript为网页添加动态效果并实现与用户交互的功能。</h5>
        <p>1. JavaScript入门篇，让不懂JS的你，快速了解JS。</p>
        <p>2. JavaScript进阶篇，让你掌握JS的基础语法、函数、数组、事件、内置对象、BOM浏览器、DOM操作。</p>
        <p>3. 学完以上两门基础课后，在深入学习JavaScript的变量作用域、事件、对象、运动、cookie、正则表达式、ajax等课程。</p>
</div>
<form>

    <input type="button" onclick="ChangeColor()" value="改变颜色">
    <input type="button" onclick="ChangeWH()" value="改变宽高">
    <input type="button" onclick="ContentHidden()" value="隐藏内容">
    <input type="button" onclick="ContentDisplay()" value="显示内容">
    <input type="button" onclick="ResetToDefault()" value="取消设置">
</form>
<script type="text/javascript">
//定义"改变颜色"的函数
    function ChangeColor(){
       var mychar1 = document.getElementById("con");
       mychar1.style.color="blue";
       var mychar2 = document.getElementById("txt");
       mychar2.style.color="blue";
    }
//定义"改变宽高"的函数
    function ChangeWH(){
       var mychar1 = document.getElementById("con");
       mychar1.style.width="800";
       mychar1.style.height="200";
       var mychar2 = document.getElementById("txt");
       mychar2.style.width="800";
       mychar2.style.height="200";
    }
//定义"隐藏内容"的函数
    function ContentHidden(){
       var mychar1 = document.getElementById("con");
       mychar1.style.display="none";
       var mychar2 = document.getElementById("txt");
       mychar2.style.display="none";
    }
//定义"显示内容"的函数
    function ContentDisplay(){
       var mychar1 = document.getElementById("con");
       mychar1.style.display="block";
       var mychar2 = document.getElementById("txt");
       mychar2.style.display="block";
    }

//定义"取消设置"的函数
    function ResetToDefault(){
   var mymessage=confirm("Are you sure you want to reset all settings to default");
   if(mymessage==true)
   {
        var mychar1 = document.getElementById("con");
       var mychar2 = document.getElementById("txt");
        mychar2.style.color = "black";
        mychar2.style.backgroundColor = "white";
        mychar2.style.width = orignWidth;
        mychar2.style.height = orignHeight;
        mychar2.style.display = "block";
   }
   else
    }
</script>
</body>
</html>