Here's how you can deactivate your Facebook account immediately so your boss doesn't see it. This is also helpful if you're doing a job search, and don't want prospective employers to find your Facebook profile.
1. Click the account menu (arrow) at the top right of the Facebook interface.
2. Go to Account Settings.
3. Select the Security option in the left side of the menu.
4. Click on Deactivate Your Account.
Your Facebook timeline and the rest of your information disappears from Facebook right away. You will not appear in searches, and people on Facebook won't be able to view your information.
To turn your account back on, just log in again and your account will be restored.