Getting off my soapbox, I've been collecting pictures of National Park Service signs that are obviously aimed at the lowest common denominator in our population. My favorite examples:

C&O Canal NP: "Know the dangers of the Potomac River - slippery rocks, hazardous currents. EVEN WADING CAN KILL!" (My husband and I are fond of pompously intoning "Even wading can kill.." at odd moments)

Cache La Poudre River, Colorado: "In case of flooding, climb to safety." Uh, duh?

Padre Island National Seashore:
1. "Danger - blue jellyfish" - no explanation, just those 3 words to warn folks that touching the dead Portuguese Man O'War jellyfish washed up on the beach is really not a good idea (they have a toxic sting that can cause some people to go into anaphylactic shock, even when dead). A few more words on the sign might make that clearer: "Danger, blue jellyfish poisonous. Do Not Touch!"
2. "Report live turtles immediately" What are the live turtles doing that they need to be reported? To whom do we report them - the FBI? (Actually, I know this is because the sea turtles that sometimes come to Padre Island to lay their eggs are endangered, and the Park Service wants to keep track of them and protect them - but does your average beach-going tourist know this, and what would THEY make of this sign?)