Give it a bit longer than 5 hours. Patience is a virtue.
To answer your question though, use the Override_URL sub to look for the domain(s) you want to block and stop the Webview from loading. This only uses the actual URL to be loaded though, not specific elements (so it won't block ads, only stop the loading of pages from certain domains)
Sub WebView1_OverrideUrl (Url As String) As Boolean
If url.IndexOf("google.com") >-1 Then
Return True
End If
End Sub
will stop any pages from google.com loading. If, however, you load any random page that has Google AdSense ads it wont stop anything.
It seems rather unethical to want to display a webpage and not the ads - unless that webpage is your own - so I won't be giving an answer for that.