XM  : Please note the term "poster" has several meanings.  I refer you to #3 which is the definition of my use of  the term.  If I be of further help, please let me know.  regards, Gary  
:  noun
1.
a placard or bill posted or intended for posting in a public place, as for advertising.
2.
a person who posts bills, placards, etc.
3.
Digital Technology. a person who posts or submits an online message to a message board:
The previous poster in this thread was off-topic.

Definition is from the "on-line" M.W. Dictionary