<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>input-placeholder</title>
</head>
<body>
<intput type="text" placeholder="请输入用户名">
<intput type="password" placeholder="请输入密码">
<intput type="email" placeholder="请输入邮箱">
</body>
</html>
输入框标签是input,而且要么<input />结束,要么以<input></input>闭合结束
“<intput>”标签打错了,应该是”<input>“