Quel sito è codificato in UTF7. Usa qualcosa di simile

codice:
        Dim objWebClient As New System.Net.WebClient
        Dim url As String = "http://www.oroscopi.com/oroscopo/oroscopo_giorno.php?segno=Cancro"
        Dim codec As New System.Text.UTF7Encoding()
        Dim html As String = codec.GetString(objWebClient.DownloadData(url))

        Dim s1 As String = "<div class=""oroscopo"">"
        Dim s2 As String = "</div>"
        Dim s12 As String = ""
        Dim x As Integer = html.IndexOf(s1)
        Dim y As Integer = html.IndexOf(s2, x)
        If x > -1 AndAlso y > -1 Then
            x += s1.Length
            s12 = html.Substring(x, y - x)
        End If
        s12 = s12.Replace("/cm/img/segni/big/cancro.gif", "cancro.gif")
        'Literal1.Text = "<pre>" & Server.HtmlEncode(s12) & "</pre>"
        Literal1.Text = s12