<!DOCUMENT html>
<html>
<head>
<meta charset="utf-8">
<title>练习看看好用吗？</title>
<style>
div{
height:100px;
width:100px;
background-color:red;
color:green;
font-size:20px;
margin-top:0px;
margin-left:0px;
}
h1{
background-color:green;
margin-top:0px;
}
body{
background-color:orange;
}
head{
}
</style>
</head>
<body>
<h1>这是第一个标题！！！</h1>
<div>你好你好</div>
</body>
</html>