﹤system.web﹥  
﹤httpruntime requestlengthdiskthreshold="256" maxrequestlength="2097151"﹥  
﹤/httpruntime﹥
﹤/system.web﹥ 

  <system.webServer>  
    <security>
      <requestFiltering>
        <!--500MB-->
        <requestLimits maxAllowedContentLength="500000000" />
      </requestFiltering>
    </security>
  </system.webServer>