Powershell Invoke-Webrequest post method - incorrect payload length - powershell

Question

I am trying to submit a form using invoke-webrequst cmdlet, and this is the code
$postParams = #{regno='1234567';dob='01/01/1997';B1='Get Marks'}
$response = Invoke-Webrequest -Uri ("http://studentresulsts/res.asp") -Body $postParams -Method Post -Debug -OutFile out.html
VERBOSE: POST http://studentresulsts/res.asp with -1-byte payload
VERBOSE: received 13-byte response of content type text/html
The $response comes back as 'Access Denied' (13-byte response)
The payload length is shown as 1-byte while $postParams is clearly more than that. Wondering if that's the reason I am getting 'Access Denied'.
Checked the form manually in browser and it works fine with correct field values.
I am using powershell 4.0
Answer : Okay, I was missing referrer URL in the header which the server was looking for, then I included referrer and it works fine :) . My new script looks like this. Thanks for your help...
$postParams = #{regno='1234567';dob='01/01/1997';B1='Get Marks'}
$headervals = #{'Referer'='http://studentresulsts/gdslplus/gdslform.htm';'Content-Type'='application/x-www-form-urlencoded'}
$response = Invoke-Webrequest -Uri ("http://studentresulsts/res.asp") -Body $postParams -Method Post -Debug -OutFile out.html

Answer 1

The fact that you don't have to manually authenticate does not mean the access isn't verified(e.g. trusted sites in IE).
Perhaps you are missing a crucial header?