The Fulham "goal" was correctly called offside, as every replay showed. Free kicks are taken rapidly like that all the time and are allowed at the referee's discretion. Whether the ball was still rolling or not (if it was, it was moving at less than snail's pace) comes into the realms of things like players not standing exactly ten yards away, players pinching five yards at free kicks or throw-ins, goalies moving off their line before the penalty kick is taken (which they routinely do) and dodgy body contact. It's a game played by human beings refereed by human beings and that's part of the beauty of it. Had Salah not scored no-one would be talking about the free kick. The fact is that Fulham were caught napping, a disgrace when none other than Mo was running free down the flank.