With more than 500 million people now on Facebook, it's inevitable that you'll be friended by someone you know, but with whom you don't want to share your online life. Once you've accepted them as a friend, how do you avoid them without the awkwardness of unfriending them?

Facebook has made it easy to hide other members' status updates. Place your mouse over an update from, say, Charlie, and a light blue X appears to the upper right corner of the update. Click the X, and Facebook will present you with three buttons from which to choose: Hide Charlie, Mark as Spam and Cancel. If you click Hide Charlie, you'll never see Charlie's updates again. (Click Spam and the message disappears and a notice gets sent to Facebook's servers and analyzed by spam filtering software.)

But how do you keep Charlie from reading your updates? Skirting your way around someone you've accepted as a Facebook friend is trickier. When you write a status update of your own, look for the lock-shaped icon below and to the right of the text input box. Click on the lock, and Facebook will pop up a menu. Click the bottom option, Customize. That will pop up a dialog box labeled Custom Privacy that lets you filter who will see your update.

There are two ways to exclude people. The quick and easy way is to type their names into the box labeled "Hide this from these people" at the bottom of the dialog box. To hide all future updates from these folks, click the checkbox at the very bottom that says "Make this my default setting." Then click the big blue Save Setting button. From now on, evil Charlie won't get your updates.The more sophisticated solution is to replace this blacklist with a list of people you do like. That way you can accept any number of new friends without having to accidentally share your updates with them.

To do this, click on Friends in the left margin of Facebook's interface. You'll see a button at the top of the Friends page labeled "+ Create a List". Click that and use the dialog box that pops up to make a list of the friends you want to share with. Call it, say, True Friends.

Next time you post an update, follow the instructions above to bring up the Customize dialog box. But instead of typing into the "Hide this" field, click the menu at the top labeled "Make this visible to these people." Select the option Specific People. A text input box will appear. Type the name of your new list, True Friends, into this field. Click "Make this my default setting" and then Save Setting. From now on, only your True Friends list will see your updates. Complicated and annoying, yes, but probably much less so than it was going to high school with Charlie.

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