Deactivating your Facebook account is a temporary action that sends your account into a dormant state. Your profile disappears from the site until you manually reactivate your account. While Facebook does not specifically tell your friends that you have elected to deactivate your account, your friends are likely to notice your absence based on the information that disappears when you deactivate.
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Notifications are red badges that appear in the top left corner of a Facebook user's screen whenever an action takes place that relates to her account. While your friends are notified when you officially accept their friend requests, they are not sent a notification if you deactivate your account. While you will go missing from their friend lists, Facebook does not send a red flag notification that points out your absence.
When you deactivate your account, the comments you previously left on a friend's page will no longer appear. She may notice that the remarks have disappeared, cluing her in to the fact that your account has been deactivated. Messages left under photos, directly on a wall or beneath a posted link all become invisible during the time that your account is deactivated on Facebook.
A deactivated Facebook account is no longer returned in search results on the social networking site. If a friend types your name in the search engine at the top of her Facebook screen and does not see your profile returned in the results, she knows that you are no longer present on Facebook. Similarly, your private messages will no longer turn up in search results in the "Messages" application.
Photos that you tag of your friends are made invisible with the rest of your profile when you deactivate your Facebook account. The number of photos associated with a friend's account, displayed next to the "Photos" tab on her profile, will be reduced when you deactivate your account. If your friend sees that the photos you tagged her in are gone, she will know that your account is not currently active on Facebook.