No "fact" can be wrong. But things that are thought of as facts are wrong.
For example, when you flush the toilet, the way the water goes down has nothing to do with what hemisphere you're on. This is a common mistake. The Coriolis effect is too small to have a significant effect on a 2-foot-long toilet bowl.
Besides the obvious one of religion, the only one I can think of is the myth that caffeine stunts your growth. This is only at the top of my mind do to being at a coffee shop earlier.
This thread seems to be more about myths than it does about facts. I have a few myths that you may or may not have known weren't true.
Bats are not blind. They have fully functional eyes, but they primarily use a sonar system to navigate through dark areas.
Strawberies are not berries. They are "accessory fruits" because they are not produced entirely from one ovary of the plant.
Cass Elliot (Mama Cass/Naomi Cohen) did not die from choking on a ham sandwich (which was commonly believed due to her weight). She died of a heart attack.
I don't think that Wikioedia is a very reliable source.
And I think that is another very common misconception. They have editors and stuff, and most articles have several sources listed at the bottom. In addition to that, articles with content which hasn't been verified or which may be partial usually have a warning saying so at the top. Sure, you shouldn't just trust everything on Wikipedia blindly, but most of it should be true, especially when it's about something like a list of common misconceptions.
Pretty much all the factual errors (or outright lies)on Wikipedia I've encountered have been results of a moderator simply missing the edit made and not removing that part.
Ah, finally found this story. It's a bit old already, but might give you an idea of the possible risks when citing Wikipedia.
Personally, I find Wikipedia perfect for quickly looking up things. Only when I'm doing more in-depth research I take my time to verify facts and check other sources myself. Otherwise eliminating the small possibility of having a false fact is not worth the time needed to do so.
Wikipedia is awesome. Anyone who says it's unreliable is either mistaken or jumping on a bandwagon or something else. As for the examples of incorrect information on wikipedia, I call spotlight fallacy.
My only problem with wikipedia is that it can be too general. Like, I've seen someone try to convince me that the red-tailed hawk was a species of hawk because wikipedia covers colloquial speech. That was just silly.
Wikipedia should mention that red tailed hawks aren't hawks on its common misconceptions page.