Watching the replay at HT, Beckford's foot is ahead of N'gog so it's off.
Nah, he's level.
edit: and that's regardless of whether Beckford touched it. He challenged the keeper so he was active.
That was directed at those saying Becchio was the one offside. We know now that it wasn't him flagged against, so it doesn't matter, but he couldn't have been offside anyway if Beckford didn't touch it.