This exception is thrown because incoming request is greater than allowed maximum request length. By default ASP.NET http runtime allows to receive requests that are not greater than 4 MB. This value can be increased by specifying maxRequestLength parameter of <httpRuntime> section of the configuration file (web.config).
1. Open the Web.config file in VS or Notepad.
2. Find the httpRuntime element in the system.web section as follows:
maxRequestLength="10000"/> (increase the marked number of bytes)
More detail information about mentioned parameters can be found in Microsoft documentation or in this blog post as well.