Now, I'm no cycling expert, but I think rule No. 1 would have to be, "Stay on the road," or, "Don't flip off your bike into the ravine." Frank Schleck, during the Tour de Switzerland, did not follow either of those rules.
And yes, it's OK to laugh -- Schleck was fine, and amazingly, got back on his bike and finished just three minutes behind the leader.
(H/T: The Sporting Blog)