myweb.MySSL obj=new myweb.MySSL(); /// u r webservice instance 

 
using System.net;

private void Button1_Click(object sender, System.EventArgs e)
  {                 

          casrv.MySSL obj=new casrv.MySSL(); /// u r webservice instance
         System.Net.ServicePointManager.CertificatePolicy = new  TrustAllCertificatePolicy();
          Response.Write(obj.HelloWorld());

 }

      public class TrustAllCertificatePolicy : System.Net.ICertificatePolicy

      {

            public TrustAllCertificatePolicy() {}

            public bool CheckValidationResult(ServicePoint sp, 

                  X509Certificate cert,

                  WebRequest req, 

                  int problem)

            {

                  return true;

            }

      }