I'll show you the basic usage of IF function in Google Drive Spreadsheet. The IF function returns one value if a specified condition evaluates to TRUE, or another value if it evaluates to FALSE.
If you are afraid of being hacked or someone else using your Facebook account you can enable option that will send you an email or text message in case your account has been accessed from a device that you never used before.
Very useful Javascript feature that can prevent a user from losing the data they are entering in an entry field or text editor in case of unintentional leaving of a page.