<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
<title>Jquery显示与隐藏input默认值_www.jb200.com</title>  
<script language="
javascript" src="jquery-1.7.1.min.js"></script>  
</head>  
<body>  
<p><input type="text" value="请输入邮箱地址" id="email" id="email" /></p>  
<p><input type="button" value="提交" /></p>  
<script type="text/javascript">  
$("#email").focus(function(){  
   var email_txt = $(this).val();  
   if (email_txt == this.defaultValue) {  
      $(this).val("");  
   }  
  })  
$("#email").blur(function(){  
   var email_txt = $(this).val();  
   if (email_txt == "") {  
      $(this).val(this.defaultValue);  
}  
})  
</script>  
</body>  
</html>