From Xojo Documentation
Called when the user modifies the HashTag in the browser address bar or when WebSession.SaveState is called.
The HashTag feature is not limited to just simple bookmarking. For example, a single page with a list of records could change the tag whenever the record changes. By implementing the HashTagChanged event, the current record can be changed only by entering the correct tag in the URL.
Displays the hash tag that the user entered in the address bar: