The GoBack method navigates the browser to the previous
page in its session history, if one is available. This is equivalent to
selecting the Back button in a standard web browser. If there is no previous
entry in the history list, the method will succeed but no navigation will
occur. The availability of backward navigation can be determined by
handling the HistoryChanged event and checking the value of the
CanGoBack property.
Calling ClearHistory will remove the session history for
the browser instance. After the history has been cleared, calling
GoBack will have no effect until new pages have been visited.