This screen can be found in Google under &34'Account Settings,&34' linked on top of a Google page, and used to set up two-step verification.

Now all Google users can take advantage of the two-step log-in procedure previously available to Google Apps customers.

The company started rolling out the option to use two-step verification to Google Account holders today, according to a blog post. The idea comes from a classic security tactic, the notion that accounts are more secure when you log in using two factors: something you know, such as a password, and something that only you have, such as your phone.

Google Apps users started using this feature in September. Account holders log in to Google as usual, but the first time they enable the two-step process they will receive a code via a voice call or text message, or they can generate their own code using a mobile app available for iPhone, Android, or BlackBerry. That code can be saved for 30 days.

Obviously it will be much harder for anyone bent on hacking your account to steal a code sent to your phone (unless you're a valuable enough target to warrant stealing your phone and hacking your password). It's an optional feature, but one strongly recommended by security experts.