Without seeing more, this could be a variety of problems. With that in mind, here is a list of possible fixes for your issue:
Cause 1
This problem occurs because the client makes an HTTP request by using
an HTTP method that does not comply with the HTTP specifications.
To resolve this problem, see resolution 1.
Cause 2
This problem occurs because a client makes an HTTP request by sending
the POST method to a page that is configured to be handled by the
StaticFile handler. For example, a client sends the POST method to a
static HTML page. However, pages that are configured for the
StaticFile handler do not support the POST method.
To resolve this problem, see resolution 2.
Resolution 1
Make sure that the client sends a request that contains a valid HTTP
method. To do this, follow these steps:
- Click Start, type Notepad in
the Start Search box, right-click Notepad, and then click Run as
administrator.
- Note If you are prompted for an administrator password or for a
confirmation, type the password, or provide confirmation. On the File
menu, click Open. In the File name box, type
%windir%\system32\inetsrv\config\applicationhost.config, and then
click Open.
- In the ApplicationHost.config file, locate the
tag.
- Make sure that all the handlers use valid HTTP methods.
- Save the ApplicationHost.config file.
Resolution 2
Send the POST request to a page that is configured to be handled by a
handler other than the StaticFile handler (for example, the ASPClassic
handler). Or, change the request that is being handled by the
StaticFile handler so that it is a GET request instead of a POST
request.
MSDN Source