How to make yourself offline on facebook?

[Sophie]

When you go onto Facebook chat, through a laptop/computer, there should be a small green icon at the top of the chat. This shows whether you're online or offline, to determine whether you're online or offline, you go onto your list of contacts and at the top, there should be a small green icon. Click on that, and it should come up with opitions. If not, you can simply unfriend this person and they cannot see your profile and message you again.
Hope this helps