What causes an HTTP 405 “invalid method (HTTP verb)” error when POSTing a form to PHP on IIS?

Question

I have one form in a PHP (5.2.9-1) application that causes IIS (Microsoft-IIS/6.0) to throw the following error when POSTed:

The page you are looking

Answer 1

I am deploying VB6 IIS Applications to my remote dedicated server with 75 folders. The reason I was getting this error is the Default Document was not set on one of the folders, an oversight, so the URL hitting that folder did not know which page to server up, and thus threw the error mentioned in this thread.