Wikipedia:Autoblock

An example of an autoblock causing collateral damage. This display makes it look like admin Curps blocked many other users (identified by anonymizing six digit numbers). In actuality, Curps only blocked one user, and all the others were "collateral damage" caught by the autoblock because they were using IPs related to the blocked user.

An autoblock is an automatic block of an IP address. Autoblocks are the result of an attempt to edit Wikipedia from an IP address recently used by a blocked user.

An example of what an autoblock looks like from the blocked user's side.

Each time a user edits Wikipedia, the IP address from which the edit was made is logged (this log is accessible only by a very small number of trusted users, called checkusers). If a blocked user attempts to edit, the IP from which they are editing is "autoblocked", to prevent their switching to editing anonymously or under a sockpuppet username.

It is possible for innocent users who have done nothing blockworthy to be blocked from editing by an autoblock. If this happens to you, simply request an unblock and an administrator will review the situation.