[DllImport("wininet.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto, SetLastError = true)]
public static extern bool InternetSetOption(int hInternet, int dwOption, IntPtr lpBuffer, int dwBufferLength);
private unsafe void SuppressWininetBehavior()
{
  /* SOURCE: http://msdn.microsoft.com/en-us/library/windows/desktop/aa385328%28v=vs.85%29.aspx
  * INTERNET_OPTION_SUPPRESS_BEHAVIOR (81):
  *   A general purpose option that is used to suppress behaviors on a process-wide basis. 
  *   The lpBuffer parameter of the function must be a pointer to a DWORD containing the specific behavior to suppress. 
  *   This option cannot be queried with InternetQueryOption. 
  *   
  * INTERNET_SUPPRESS_COOKIE_PERSIST (3):
  *   Suppresses the persistence of cookies, even if the server has specified them as persistent.
  *   Version: Requires Internet Explorer 8.0 or later.
  */
  int option = (int)3/* INTERNET_SUPPRESS_COOKIE_PERSIST*/;
  int* optionPtr = &option;
  bool success = InternetSetOption(0, 81/*INTERNET_OPTION_SUPPRESS_BEHAVIOR*/, new IntPtr(optionPtr), sizeof(int));
  if (!success)
  {
    MessageBox.Show("Something went wrong !>?");
  }
}