By default, IIS web server allows for limited file size to be uploaded to the web server. For IIS 5 and IIS 6, the default maximum file upload size is 4 MB. If a user uploads a file larger than 4MB, they'll get an error message: "Maximum request length exceeded.".
In IIS 5.0 and 6.0, The httpRuntime web.config element controls settings about how ASP.NET processes requests, including maximum request length. It is controlled by the following attribute:
This allows a file upload of 1 GB and it will time out after 100,000 seconds, or 27.8 hours.
If you have successfully modified the maxRequestLength attribute but still cannot upload large files, please check the IIS Large File Upload Debugging Guidelines.