title: POST requests to ASP site don't bring a good result
body: <p>I try to create POST request to ASP site (just like in Firefox), for get JSON response.<br>
  But in my code response is html, not JSON.</p>
  
  <p><a href="http://www.polskieradio.pl/10,Czworka" rel="nofollow">link to site</a></p>
  
  <p>Firebug Response Headers:</p>
  
  <pre><code>HTTP/1.1 200 OK
  Cache-Control: private
  Content-Type: application/json; charset=utf-8
  Server: Microsoft-IIS/7.5
  X-AspNet-Version: 4.0.30319
  X-Powered-By: ASP.NET
  Date: Mon, 08 Sep 2014 11:32:22 GMT
  Content-Length: 101
  </code></pre>
  
  <p>Firebug Request Headers:</p>
  
  <pre><code>POST /Portal/WebPageMethods/Playlista/playlist.aspx HTTP/1.1
  Host: www.polskieradio.pl
  User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:30.0) Gecko/20100101 Firefox/30.0
  Accept: application/json, text/javascript, */*; q=0.01
  Accept-Language: pl,en-US;q=0.7,en;q=0.3
  Accept-Encoding: gzip, deflate
  Content-Type: application/x-www-form-urlencoded; charset=UTF-8
  X-Requested-With: XMLHttpRequest
  Referer: http://www.polskieradio.pl/10,Czworka.json
  Content-Length: 17
  Cookie: cookies-accepted=true; ASP.NET_SessionId=35p3kig5t5cmlikubnlnytlh
  Connection: keep-alive
  Pragma: no-cache
  Cache-Control: no-cache
  </code></pre>
  
  <p>source code:</p>
  
  <pre><code>import requests
  import json
  
  url = "http://www.polskieradio.pl/Portal/WebPageMethods/Playlista/playlist.aspx?program=4&amp;count=1"
  payload = { "Host": "www.polskieradio.pl",
          "User-Agent": "Mozilla/5.0 (X11; Linux x86_64; rv:30.0) Gecko/20100101 Firefox/30.0",
          "Accept": "application/json, text/javascript, */*; q=0.01",
          "Accept-Language": "pl,en-US;q=0.7,en;q=0.3",
          "Accept-Encoding": "gzip, deflate",
          "Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",
          "X-Requested-With": "XMLHttpRequest",
          "Referer": "http://www.polskieradio.pl/10,Czworka",
          "Content-Length": "17",
          "Cookie": "cookies-accepted=true; ASP.NET_SessionId=5l1eezrjfdyvvevxushojtc2",
          "Connection": "keep-alive",
          "Pragma": "no-cache",
          "Cache-Control": "no-cache"
          }
  r = requests.post(url, data=json.dumps(payload))
  print(r.headers['content-type'])
  print r.content
  </code></pre>
  
  <p>How to do this properly?<br>
  Thanks for answers!</p>