As far as I am concerned, one of the biggest myths is present not because of misunderstood rules, but mainly is fueled by human nature. People have a strong tendency to see what they want to see. When an official sees something else, the natural reaction is disbelief, often followed by anger. Their conclusion is the myth:
THE REFS ARE CHEATING AGAINST US!
When we consider the fact that the vast majority of people watching a game have, at best, a passing acquaintance with the vast majority of the rules, it is fair to say that the problem is increased exponentially. It is not uncommon after a close game to hear followers of both teams to be heard to say, "It was 5 against 7 (or 8) for our guys." But many of these are the same people who, following a whistle, are heard to shout, "No, he didn't," then turn to the person next to them and ask "What was the call?"