效果：
实现：
<!DOCTYPE html>
<html>
<head>
<title>使用CSS来渲染HTML的表单元素</title>
<style type="text/css">
input[type=text], select {
width: 100%;
padding: 12px 20px;
margin: 8px 0;
display: inline-block;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
input[type=submit] {
width: 100%;
background-color: #4CAF50;
color: white;
padding: 14px 20px;
margin: 8px 0;
border: none;
border-radius: 4px;
cursor: pointer;
}
input[type=submit]:hover {
background-color: #45a049;
}
div {
border-radius: 5px;
background-color: #f2f2f2;
padding: 20px;
}
</style>
</head>
<body>
<div>
<!-- 自己还不会写php -->
<form action="https://www.runoob.com/action_page.php">
<label for="fname">First Name</label>
<input type="text" id="fname" name="firstname" placeholder="Your name..."> <label for="lname">Last Name</label>
<input type="text" id="lname" name="lastname" placeholder="Your lastname..."> <label for="country">Country</label>
<select id="country" name="country">
<option value="australia">Australia</option>
<option value="canada">Canada</option>
<option value="usa">USA</option>
</select> <input type="submit" value="Submit">
</form>
</div>
</body>
</html>