Facebook features a built-in instant messenger that you can use to chat with friends who are online at the same time you are. Sometimes you may want to hide your online status from certain friends so they cannot chat with you. You can do this by creating a custom list on Facebook and appearing offline to that list. A list may include as many friends as you want, and you can just as easily reappear online if you do want to chat.
Open a Web browser and go to Facebook. Enter your log-in information into the "Email" and "Password" fields in the top-right. Click "Login."
Click on "Friends" on the left side of the Web page, below your profile picture.
Click the "Edit Friends" button at the top of the page to enter the "Friends" page. Click on the "Create List" button at the top of the page. The "Create New List" dialog box will appear.
Enter "Blocked on Chat" into the "Enter a Name" field.
Scroll through the list of friends in the dialog box and click on each one of the friends who you want to block. Click "Create List" at the bottom of the dialog box.
Click on the "Chat" bar at the bottom-right corner of your Facebook page to open your chat list. This list shows all friends currently online that you can chat with and who can see you.
Click the "Friend Lists" drop-down menu at the top of your chat window and select the "Blocked on Chat" list.
Hover over the green slider button to the right of "Blocked on Chat." Your cursor will read "Go Offline." Click the slider; it will turn gray and you will appear offline to any friends in this list.
Add as many friends as you want to the "Blocked on Chat" list by clicking on the list on the left side of the "Friends" page. Click the gray slider bar to the right of "Blocked on Chat" on your chat window to turn the slider green and appear online to the friends on the list.