Internet

If ever there was a rule to live by...

... then this is it. A poster produced by the British government during the second world war, as Boing Boing says, so much different from the government of today with their "OMG TERRISTS GONNA KILL US ALL ZOMG ZOMG ALERT LEVEL BLOODRED RUN RUN TAKE OFF YOUR SHOES MOISTURE BOMBS ZOMG!".