New Post: Big error 404 file not found

oh! my god

I find the solution and i don't understand why but

last week i try to enlarge the maximum upload for the file to 30Mb

i modify the web config adding in system.webServer

<requestFiltering>
        <requestLimits maxAllowedContentLength="30720" />
      </requestFiltering>
    </security>

and modify

<httpRuntime shutdownTimeout="120" executionTimeout="900" useFullyQualifiedRedirectUrl="true" maxRequestLength="12288" requestLengthDiskThreshold="12288" requestPathInvalidCharacters="&lt;,&gt;,*,%,:,\,?" requestValidationMode="2.0" />

to

<httpRuntime shutdownTimeout="180" executionTimeout="900" useFullyQualifiedRedirectUrl="true" maxRequestLength="30720" requestLengthDiskThreshold="30720" requestPathInvalidCharacters="&lt;,&gt;,*,%,:,\,?" requestValidationMode="2.0" />

restoring the old web.config all go well!!!!
But I'm interested to know why is possible that this can make this error!!!!!!
very strange
but I have solved!
Thanks for all your support!
Fabio