try to send mail... it shows error like that what to do

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class sms : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    public void send(string uid, string password, string message, string no)
    {
        HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create("http://ubaid.tk/sms/sms.aspx?uid=" + uid + "&pwd=" + password + "&msg=" + message + "&phone=" + no + "&provider=fullonsms");
         
        HttpWebResponse myResp = (HttpWebResponse)myReq.GetResponse();
        System.IO.StreamReader respStreamReader = new System.IO.StreamReader(myResp.GetResponseStream());
        string responseString = respStreamReader.ReadToEnd();
        respStreamReader.Close();
        myResp.Close();
    }

    protected void btnSendSms_Click(object sender, EventArgs e)
    {
        if (Page.IsValid)
        {
            string yourmobilenumber = "yourmoblienumber";
            string yourpassword = "yourpassword";
            send(yourmobilenumber, yourpassword, txtMessageBody.Text, txtRecipient.Text);           
        }
    }
}