Right, so it's about time I cleared the air with this, and what's going on in regards to claim distances.
First off, as to why you were placed in webjail: After repeated warnings from myself to move away from the claim, you continued to dig and mess with the landscape around it... simply, it was just disrespect.
The general rule at the moment, though not clearly stated, is to have that basic form of respect to other players, and to not build within 100 blocks unless given permission, as Jack said.
With that said, we are now working on setting up a claim distance through the GreifPrevention plugin so instead of a rule, it will just be part of the server. Most likely, there will be between a 50-100 block distance set in between claims.