It is an advantage to take a screenshot of any Avast Alert window, with the See details option open as there really isn't enough to work with.
Web Shield alerts are alerting on Web Sites so wouldn't be sending anything to the quarantine (its blocked).
Only File Shield alerts of files on your system would be sent to Quarantine. In which case you can get details on the alert from the Quarantine on that detection.
For Web Shield Alerts they might still be recorded in the Notifications Area, see attached image.