Pilloried for the decisions they give and castigated for the ones they don't, referees do not have an easy job.
These days it's even harder, as technology allows their every decision to be dissected and discussed by the watching public.
However, some calls are just so bad, they deserve to be pulled apart time and time again.
Over the following slides, we look at 20 controversial refereeing decisions. There's "ghost goals," handballs, feigned injuries and, of course, Graham Poll's three yellow cards at the 2006 World Cup.
Organised in chronological order, this is not an all-encompassing list, so feel free to add your own refereeing gaffes in the comments section below.