IIS使用ISAPI_REWRITE3返回503代码
#for 3.xRewriteCond %{HTTP:Host} ^.*abc\.net.*$
RewriteRule (.*) /503.asp 503.asp<%
Response.Status="503 Service Temporarily Unavailable"
%><!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>503 Service Temporarily Unavailable</title>
</head><body>
<h1>Service Temporarily Unavailable</h1>
<p>The server is temporarily unable to service your
request due to maintenance downtime or capacity
problems. Please try again later.</p>
</body></html>---- 503.php<?php
ob_start();
header('HTTP/1.1 503 Service Temporarily Unavailable');
header('Status: 503 Service Temporarily Unavailable');
header('Retry-After: 3600');
header('X-Powered-By:');
?>
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>503 Service Temporarily Unavailable</title>
</head><body>
<h1>Service Temporarily Unavailable</h1>
<p>The server is temporarily unable to service your
request due to maintenance downtime or capacity
problems. Please try again later.</p>
</body></html>如果有IIS的控制权，可以为站点建一个独立的应用程序池，然后把应用程序池暂停也可以。
