📄 notmodified.srf
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{{ handler NotModified.dll/Default }}
<html>
<!-- (c) 2000 Microsoft Corporation -->
<head>
<title>{{Title}}</title>
<meta http-equiv="content-type" content="text/html; charset=iso8859-1">
<link rel="stylesheet" href="normal.css" type="text/css">
</head>
<body>
<h1>{{Title}}</h1>
<h2>Page Created : {{NotModified}}</h2>
<h3>Instructions</h3>
<p>
Hit <a href="javascript:location.reload()">Refresh</a>
repeatedly and see how long it takes before the page creation date changes.
(Answer: The page will change after 1 minute if client-side caching is enabled,
or immediately if it's not enabled.)
</p>
<h3>How It Works</h3>
<p>
The server compares the value of the HTTP_IF_MODIFIED_SINCE request header
with the current time. If less than 1 minute has passed, the server returns
a 304 (Not Modified) status code without generating a response body.
If more than 1 minute has passed, or the HTTP_IF_MODIFIED_SINCE
header wasn't present in the request, the server generates the response in the
standard way and sets the 'Last-Modified' response header with the current
server time.
</p>
<hr></hr>
<h2>Details</h2>
<p>
This sample demonstrates the use of the 304 (Not Modified) HTTP status code.
</p>
<p>
Use this status code when:
<ul>
<li>The client has performed a conditional GET request.</li>
<li>Access to the resource is allowed.</li>
<li>The content cached by the client is up to date.</li>
</ul>
</p>
<p>
Benefits:
<ul>
<li>
Performance: The server avoids generating a response body and transmitting that data over the wire.
</li>
</ul>
</p>
<p>
Response Requirements:
<ul>
<li>Do not send a body.</li>
</ul>
</p>
<p>
To make use of this status code:
<ul>
<li>
Append a 'Last-Modified' header and/or an 'ETag' header to a successful (200 OK) response for this resource.
This supplies the client with the information it needs to enable it to make conditional requests.
</li>
<li>
Check the HTTP_IF_MODIFIED_SINCE and/or HTTP_IF_NONE_MATCH request headers.
You should receive a request containing a HTTP_IF_MODIFIED_SINCE header if the client cached
a response that contained a 'Last-Modified' header.
You should receive a request containing a HTTP_IF_NONE_MATCH header if the client cached
a response that contained an 'ETag' header.
</li>
<li>Use HTTP_IF_MODIFIED_SINCE for time-based validation of the cached content.</li>
<li>Use HTTP_IF_NONE_MATCH for other validation of the cached content (the meaning of the ETag is decided by the server).</li>
</ul>
</p>
<p><i>
The information presented here is simplified for developers using
ATL Server on IIS 5.0. A requirement may be omitted if it is handled
by this platform without user intervention.
For complete information on this status code, see the
<a href="http://www.ietf.org/rfc/rfc2616.txt">HTTP 1.1 specification.</a>
</i></p>
</body>
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