John Green of Mental Floss is back with perhaps his most important list video yet: 38 common spelling and grammar errors. It’s a great lesson (or refresher course, depending on how much attention you paid in high school English) that pretty much everyone could use.

If you can’t spare nine minutes, at the very least, skip ahead to 5:15. Watch until the 5:40 mark, and run it back. Do this as many times as it takes to figure out the difference between your/you’re, there/their/they’re and it/it’s. The world would be a better place if everyone did that.