It returns something but not your resource

It is some kind of redirect so you will have to compare the response too. The webmaster has decided to show a 'not found' custom page instead of a plain 404 Error.
Code:
        Try
            Dim myResponse As Net.WebResponse = Nothing
            Dim myWebRequest As Net.HttpWebRequest = Net.HttpWebRequest.Create("http://finismundi.mforos.com/1698374/8528351-habilitar/")
            myResponse = myWebRequest.GetResponse


            MessageBox.Show(myResponse.ResponseUri.ToString)

            If myResponse.ResponseUri.ToString <> "http://finismundi.mforos.com/1698374/8528351-habilitar/" Then
                MessageBox.Show("Resource does not exist")
            Else
                MessageBox.Show("Resource exists")
            End If

        Catch ex As Exception
            MessageBox.Show("Resource does not exist")
        End Try