As any additions / changes to the Hosts File can / will be removed using a System Restore point dated before the work was done with the file, it may be a good idea to create Restore Points before and after any changes are made to the Hosts File, see the tutorial at the link below. System Restore Point - Create
It would also be advisable to clear the DNS Resolver Cache
whenever you finish working with the Hosts File, open an elevated command window
and type "ipconfig /flushdns" (without the quotes) and hit enter.