Whenever I add this line to my web.config in the system.webServer section:
With our without properties, IIS 7.5 just se
I had this exact problem and solved it by unlocking the serverRuntime
section of the applicationHost config. Command to run at console:
%windir%\system32\inetsrv\appcmd unlock config -section:system.webServer/serverRuntime
So you are actually adding this to your web config?
<location path="Default Web Site">
<system.webServer>
<serverRuntime enabled="true"
frequentHitThreshold="1"
frequentHitTimePeriod="00:00:20" />
</system.webServer>
</location>
There are several important things to bear in mind...
Further reading on MSDN
http://msdn.microsoft.com/en-us/library/aa347568%28VS.90%29.aspx