Wikipedia:Mistakes are allowed

While editors work on Wikipedia, mistakes are not only allowed but inevitable. Perfection is impossible.

Mistakes may not be acceptable if:
 * They are purposeful (which means they are not mistakes)
 * They occur a reasonable period of time after one has been warned that similar actions were mistakes
 * If they regard biographies of living people

However, mistakes may not be used to:
 * Prove that someone is unqualified to edit pages regarding a topic

Mistakes should be met with counsel, not criticism. Before banning or blocking someone, ask them what happened, and look at how long they've been an editor. If they're new, it might have been a mistake.