Softminer.net

<?php
 print date('D, d M Y H:i:s T');
?>
Browser to:

http://localhost/date.php

----------------------------------------------------------------------------------

you see that page is cached after 3 calls, if you setup cache rules in web.config

CACHING INTRICACIES

Even if you enable Output Caching, IIS does not immediately cache a request.
It must be requested a few times before IIS considers a request to be "cache worthy".
Cache worthiness can be configured via the ServerRuntime section described in this
MSDN article.

http://msdn.microsoft.com/en-us/library/ms690574

By default, when you create a cache rule a page is cached when it is requested 2 
times within a 10 second time period. 
You can change these default values by first making a change to your 
applicationHost.config file and then updating your web.config file. 
Your applicationHost.config file is typically in the 
c:\Windows\System32\inetsrv\config 
directory and is most easily opened with Notepad from a command prompt 
with administrator privileges.
In that file, find the following entry
(a child of the  element):
. Change Deny to Allow and save the file.

<sectionGroup name="system.webServer">
    <section name="serverRuntime" overrideModeDefault="Allow" />
 </sectionGroup>

----------------------------------------------------------------------------------
Then in web.config 

Refrence


<configuration>
   <system.webServer>
      <serverRuntime frequentHitThreshold="3" frequentHitTimePeriod="00:00:20" />
      <caching>
         <profiles>
            <add extension=".php" policy="DontCache" 
kernelCachePolicy="CacheForTimePeriod" duration="00:05:30" />
         </profiles>
      </caching>
   </system.webServer>
</configuration>
and finally to view the files in cache following command should be run

netsh http show cachestate

Refrence