Hello,
such repeated reports are usually popping up because browsers often remember your browsing history and attempt to access such pages in some cases. Typically this happens when you create a new tab, or type something into a search bar. The browser likes to pre-load stuff it thinks you will need, and this means that sometimes a web page that has been accessed long time ago can be re-loaded by the browser again and again.
While Avast Web Shield protects you, and you should be safe, the popups are very annoying; but there is no good solution for this on our part. It is typically enough to clear your browser's caches and/or history, so that the browser forgets the page and stops loading it.
Kind regards,
Ondrej Kolacek