HPM-Board

With the server being all fancy and updated, it wont let me on with the new upgrade. Could i downgrade my Minecraft and still get on the server?

Actually we are running Minecraft beta 1.3_01.
I think i wrote it to the news board.

I knows it's on 1.3_01 but I can't get on the server with the new upgrade thing. I wondered if I could downgrade it but still get on the server.