The site you are using as a sample page requires the NTLM authentication. You can see this by looking at the returned HEADER fields. For example curl -I http://www.dogus.edu.tr/dusor/FrmMain.aspx
returns:
HTTP/1.1 401 Unauthorized
Content-Length: 1293
Content-Type: text/html
Server: Microsoft-IIS/7.0
WWW-Authenticate: Negotiate
WWW-Authenticate: NTLM
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Date: Mon, 07 Apr 2014 21:24:09 GMT
The line WWW-Authenticate: NTLM
says, which authentication method is used. I think the answer to this question Use python mechanize to log into pages with NTLM authentication will help you.