HTTP 404 error. please help

When i tried to log into my application.. i got this error. 'the request failed with http status 404: not found.' i didnt get this error before.. but after i re-formatted my computer.. this error came up. can someone please help me? private void BtnLogin_Click(object sender, EventArgs e) { CustomerMS.localhost.Service1 cms = new CustomerMS.localhost.Service1(); ds = cms.GetUserInfo(txtUser.Text.Trim(), txtPwd.Text.Trim());--> error came from this line. uid = txtUser.Text.Trim(); pwd = txtPwd.Text.Trim(); //ds1 = cms.GetUser(txtUser.Text.Trim(),txtPwd.Text.Trim()); if ((int)ds.Tables["User Information"].Rows[0].ItemArray[0] > 0) { this.Hide(); frmMain frmmain = new frmMain(); frmmain.Show(); } else { MessageBox.Show("You didn't enter the right ID or Password", "Invalid ID or Password", MessageBoxButtons.OK , MessageBoxIcon.Error); } }