Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button3.Click
        WebBrowser1.Navigate( _
        "http://www.wetter.com/v2/index.php?SID=&LANG=DE&LOC=7004&LOCFULL=7000" & _
        "search=" & TextBox1.Text)
End Sub

Private Sub WebBrowser1_Navigated(ByVal sender As Object, ByVal e As _
  System.Windows.Forms.WebBrowserNavigatedEventArgs) Handles _
  WebBrowser1.Navigated
 
Dim HTMLCode as string = WebBrowser1.DocumentText
 
'Hier machst Du mit dem HTML-Code was auch immer Du willst.
'Wenn Du den HTML-Code fertig bearbeitet hast, schreibst Du ihn zurück in das 
' Control
 
WebBrowser1.DocumentText = HTMLCode
End Sub