Como ele está indo até agora?
Yours is a shortened form of "How is (going) so far?", certainly the question made by Stranger invites some further details about the Facebook page. For instance, if You finished up the page, if you have attached photos, have a scrapbook, if people have "nudged" You. Perhaps "Stranger" wants to know if he/she would like to invite him to be added to "You" buddy list.
The question rings, to me, as a general way to engage in small talk, to show interest in which somebody else is doing. A genuine interest, I mean.