Problem retrieving data with Webclient

Hi to everyone,i have a problem with my app that should retrive data from some websites.

I use this code to make a http POST request but i don't retrieve the correct data,probably because the website use iframes

The code I use is:

public static string HttpPost(string URI, string Parameters)

{

try

{

System.Net.WebRequest req = System.Net.WebRequest.Create(URI);

req.ContentType = "application/x-www-form-urlencoded";

req.Method = "POST";

byte[] bytes = System.Text.Encoding.ASCII.GetBytes(Parameters);

req.ContentLength = bytes.Length;

System.IO.Stream os = req.GetRequestStream();

os.Write(bytes, 0, bytes.Length);

//os.Close();

System.Net.WebResponse resp= req.GetResponse();

if (resp == null) return null;

System.IO.StreamReader sr = new System.IO.StreamReader(resp.GetResponseStream());

return sr.ReadToEnd().Trim();

}

catch (Exception ex) { }

return null;

}

-----------------------------------------

// naviga();

Http.Post("http://89.137.253.14/Iast.php", new NameValueCollection() {

{ "imei", "013270000134001" }

});

As you can see if you make a direct GET or POST reuest using the url on the Form you receive a page error and that is what i receive using my app.

It's only a website example and if someone can help me i will happy to contribute with a donation too.

I need to receive the complete source page like using a browser

Thanks