San Diego, California (CNN) The good folks at Snopes.com, the Internet's oldest and best-known fact checker, know a thing or two about debunking myths. Founder David Mikkelson and his band of web sleuths have been doing that for two decades .

You'd think once a myth or falsehood was completely debunked by Team Snopes, you would never see that bit of fake news ever again.

Well, you'd be wrong.

Here are five fake stories Team Snopes has to debunk over and over again.

1. Facebook wants you to post a privacy notice

Whenever this Facebook falsehood pops up it spreads like wildfire online: Something in your Facebook news feed says you must post a legal notice or you'll lose copyright control of your pictures and other content you share with your circle of family and friends.

Your mom, pastor, best friend from high school and seemingly everyone else has probably posted this at one time or the other. Maybe you have, too.

Another big one: Facebook is going to charge you to keep your profile private.

For the record, they're both false. So the next time either appears in your Facebook feed, you can ignore it.

2. Something's on your windshield

This one is as old as urban legends themselves and usually goes like this: Late at night someone goes out to his or her car on a quiet street or in a deserted parking lot. After they get in, they notice a piece of paper or money or (insert your shiny object here) attached to the windshield. They get out of the car to investigate and are suddenly jumped by gang members or creepy clowns or (insert your bad guy of choice here).

The newest version of this golden oldie involves a piece of clothing tied to the wiper blades and women being grabbed by human traffickers.

It's just a myth, and one that particularly galls Mikkelson.

"None of this really makes any sense. First off, if you're looking to jack a car, it's a crime of opportunity. You're not going to put stuff on cars and then sit in the parking lot waiting for those people to come back, because you don't know when they're coming back," he says. "Why do you need someone to get in their car and then get out again so you can carjack them? Why not just do it when they're entering their car? It makes no sense as a crime scheme."

3. ATMs have panic codes

You're being robbed and the thugs have taken you to an ATM to force you to withdraw your hard-earned cash. But you turn the tables by punching your PIN number in reverse order, alerting the ATM to send an alarm to the cops.

There's actually a bit of truth to this one. A Chicago businessman dreamed up the idea and had it patented back in the '90s. He pitched it to the banks for years, but they weren't interested and the technology was never developed. So no, entering your PIN number in reverse to alert the police doesn't work.

Besides, some of us couldn't tap out our PIN numbers in reverse under the best of circumstances, much less with a gun pointed at us.

4. Planetary alignment decreases gravity

Now this one's just plain weird. This hoax, which dates back to the 1970s, claims that whenever Earth lines up perfectly with Jupiter and Pluto, the combined gravitational pull from the two planets temporarily reduces gravity on Earth, allowing people to jump in the air and float, sometimes for as long as five minutes.

The last time this story made the rounds on social media it was supposed to happen on January 4, 2015. It didn't. And it won't happen in the future. But that hasn't stopped people from asking Snopes about it.

5. Red Bull contains bull semen

And the less said about this one the better.