The back button in the browser functions in the normal way -- namely going back to the previous url address that you viewed in that window during the current session.
Using the browser's back button can cause issues when trying to remember that state of the local data and that which has been saved to the server. Remember that unless you click on the save button - edits are not yet saved to the server -- so it's a good idea to get into the habit of saving your edits before clicking on the back button.
Not sure if you were using the "show preview" button -- which does not save the changes to the server -- so watch out for this one as well. The preview button is intended to check whether you're happy with the layout before saving changes to the server.
Pretty soon you'll get the hang of how this works. I'm pretty impressed with your user page - you're showing early signs of becoming a wiki guru!