Now that referees are getting video assistance, surely the number of gaffs will decrease, but there have been some howlers in the past.
The earliest I recall actually seeing was coincidentally in a world cup finals, in the USSR v. El Salvador group game. USSR defender lamped the ball out of play for a clear ES throw in, but the quick witted Soviet then collected the ball and threw it in himself, to one of his own side, who ran through and scored with the referee gleefully waving the play forward. As Boney M once said: 'Oh, Those Russians'... The poor old El Salvadorians went to war with Honduras as a result of qualifying, so I guess incompetent refs weren't top of their hate list. Not currently available online, the youtube record of this has disappeared
Through Ram-tinted spectacles there is the 1976 FA Cup semi, which I've written before was the turning point in Derby's fortunes, wherein (for those younger and/or less bitter than I) Jack Taylor gave Nish offside for playing the ball over the Man U defence TO HIMSELF before netting the ball.
Another one from that era, which possibly cost Leeds Utd TWO Championships was the 'Tinkler Incident' when West Brom were awarded a goal despite Colin Suggett and Geoff Astle being clearly offside (20 yards or so in Sugget's case) at different stage of the build up to WBA's first goal. The aftermath is a good example of what nasty pieces of work the then Leeds team were, albeit on this occasion they were 100% justified in their protests IMO!
Anyone got any other howlers to brighten up our wait for the Belgium game?....
Oh yes, another one, feb 1973 Spurs v Man City, our friend Frannie Lee scores in 'hand of god' style but less subtle, punching the ball into the spurs goal and looking damned sheepish as the ref gave the goal and the Spurs defence went ballistic. Currently on youtube in lo res colour, I recall it in hi res black and white both on TV and all over the papers the next day