regarding facebook messages?

[Arjya]

in the new look of facebook messages....for some one on the friend list on the left, the name is displayed in black and that person's profile cant be opened.............in another case i found its written "Facebook User" instead of the name.......the chats are displayed though in both the cases....what is the problem....???

thank you
thank you for the answers
actually i dont know about the ones showing names in black
but for the one showing "Facebook User" i have been told she deactivated the acc........please can you be sure about whether it really means blocking.....??