Spring_Faun

I tried joining a multiplayer server, although when I did was disconnected and I got an error message that said "The following microblocks are not installed on this client: tile.iron" Is there any way that I can add this missing microblock? If not, could anyone tell me how to switch back to 1.0.5? I have no idea to change my game versions, and I'd like to see if it would help fix the problem.