HTTP Error 404.15 – Not Found: The request filtering module is configured to deny a request where the query string is too long

Use Case

Query string exceeds reasonable size for HTTP GET.

Solution

Quick and dirty solution is to increase the maximum querystring size by setting the maxQueryString attribute on the requestLimitselement in the system.webServer/security/requestFiltering configuration section in your application’s web.config:

<system.webServer>
    <security>
        <requestFiltering>
            <requestLimits maxQueryString="NEW_VALUE_IN_BYTES" />
        </requestFiltering>
    </security>
</system.webServer>

http://mvolo.com/blogs/serverside/archive/2007/12/08/IIS-7.0-Breaking-Changes-ASP.NET-2.0-applications-Integrated-mode.aspx

Or use HTTP POST, if you can.