The trick, as All Facebook reports, is a new Advanced Settings option sitting at the bottom of the Facebook chat sidebar; to access it, just click the little gear icon and select “Advanced Settings.” (Don’t see the Advanced Settings option? Be patient; Facebook might not have enabled it for your account yet.)
Once the Advanced Chat Settings window opens, you’ll get three options: to let all your friends see you’re available for chat except for specific friends and friend lists; to allow only specific friends and lists see you’re online; or to go completely offline for chat.
For example: click the “All your friends see you except…” option, then type the names of individual friends or entire friend lists; click Save, and you’ll become invisible to those chat buddies, and only those chat buddies. (Interestingly enough, I found that I could add only certain types of friend lists in Advanced Chat Settings; “Close Friends” and “Acquaintances” were fine, as well as any custom lists that I’d created, but work- and school-oriented “smart” lists didn’t work. Odd.)
Don’t want to bother with the Advanced Chat Settings menu? Another option is to simply click a name in the Facebook chat bar, click the gear icon at the top of the chat window that appears, and select “Go Offline to [name].”
It’s a nice shortcut, but what if you forget which of your Facebook friends can see you in chat, and which can’t? Just open the Advanced Chat Settings menu, and you’ll see the names of all the chat friends you’re hiding from in the “All your friends see you except” field. Once you’re feeling chatty again, click the little “x” next to a name or list to clear it out.
Source: All Facebook
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