1、加随机数刷新界面
<td colspan="2" align="right"><img src="index.php?p=admin&c=login&a=captcha" width="145" height="40" alt="CAPTCHA" border="1"
onclick= this.src="index.php?p=admin&c=login&a=captcha&"+Math.random()
style="cursor: pointer;" title="看不清？点击更换另一个验证码。" />
</td>
demo：
<!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>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link href="application/views/admin/styles/general.css" rel="stylesheet" type="text/css" />
<link href="application/views/admin/styles/main.css" rel="stylesheet" type="text/css" />
<style type="text/css">
body {
color: white;
}
</style>
</head>
<body style="background: #278296">
<form method="post" action="index.php?p=admin&c=login&a=signin" name='theForm'>
<table cellspacing="0" cellpadding="0" style="margin-top: 100px" align="center">
<tr>
<td></td>
<td style="padding-left: 50px">
<table>
<tr>
<td>管理员姓名：</td>
<td><input type="text" name="username" /></td>
</tr>
<tr>
<td>管理员密码：</td>
<td><input type="text" name="password" /></td>
</tr>
<tr>
<td>验证码：</td>
<td><input type="text" name="captcha" class="capital" /></td>
</tr>
<tr>
<td colspan="2" align="right">
</td>
</tr>
<tr><td colspan="2"><input type="checkbox" value="1" name="remember" id="remember" /><label for="remember">请保存我这次的登录信息</label></td></tr>
<tr><td> </td><td><input type="submit" value="进入管理中心" class="button" /></td></tr>
<tr>
<td colspan="2" align="right">» <a href="../" style="color:white">返回首页</a> » <a href="get_password.php?act=forget_pwd" style="color:white">你忘记了密码吗？</a></td>
</tr>
</table>
</td>
</tr>
</table>
<input type="hidden" name="act" value="signin" />
</form>
</body>
