一：效果图预览：
1)默认：
2）当点击姓名文本框或密码文本框时，效果如下图：
3）当点击内容文本区域时，效果图如下：
二：代码如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title></title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<script type="text/javascript" src="<%=basePath %>js/jquery-1.4.4.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$(':input').focus(function(){
$(this).addClass("focus");
if($(this).val()==this.defaultValue){
$(this).val("");
}
}).blur(function(){
if($(this).val()==""){
$(this).val(this.defaultValue);
}
$(this).removeClass("focus");
});
});
</script>
<style type="text/css">
*{padding:0;margin:0;}
body {font-size:12px;font-family:"宋体";}
form {width:500px;position:absolute;top:50%;left:50%;;margin:-70px 0 0 -250px;}
fieldset {border:2px solid #458B00;padding:12px;}
legend {font-size:15px;font-weight:bold;padding:10px;color:green;}
div {padding:5px 0;}
label {color:green;}
input {height:25px;border:1px solid #A2B5CD;width:200px;font-size:12px;font-family:"宋体";padding:0px;color:green;}
textarea {width:200px;height:100px;border:1px solid #A2B5CD;font-size:12px;font-family:"宋体";padding:5px;vertical-align:middle;color:green;}
.focus {border:1px solid green;background:#eee;}
</style>
</head>
<body>
<form action="" method="post">
<fieldset><!-- 这个标签表示设置边框 -->
<legend>个人信息</legend>
<div><label for="username">姓名：</label><input type="text" id="usrename" value="天成"></div>
<div><label for="pass">密码：</label><input type="password" id="pass" value="123"></div>
<div><label for="content">内容：</label><textarea id="content">内容</textarea></div>
</fieldset>
</form>
</body>
</html>