HttpWebRequest over SSL

public static bool
AcceptAllCertificatePolicy(
    object sender,
    X509Certificate certificate,
    X509Chain chain,
    SslPolicyErrors sslPolicyErrors)
{
    return true;
}

The returned value determines whether the specified certificate is accepted for authentication.

Then set:

ServicePointManager.ServerCertificateValidationCallback
 += AcceptAllCertificatePolicy;

From here