Necroposting is a online forum term for dragging up or quoting very old or 'dead' posts or threads. It is strongly discouraged as it basically ends up in a whole load of reposts.
Also quote a whole load of pictures is also discouraged for the.same reasons, it clogs up the forum.
For future reference, if you absolutely have to comment on something three years old, just say something along the lines of...
"Nutser, I saw your first post on this thread of your M14 and MP5s and they're very nice"
However the chances are he won't have them anymore and so mentioning something from three years ago is fairly pointless...