How do I list all the incorrect word usages found in Web posts?

Since getting people to correct their grammar is about like getting them to eat their vegetables, let’s go with the rule of 3-5 servings per day.

Your is possessive. “Is that your car?”
You’re is a contraction of you are. “You’re crazy!”
Just remember: You’re touching your toes.

Its is possessive. “The group dropped its lawsuit.”
It’s is a contraction of it is. “It’s about time you got home!”
Just remember: It’s fun to watch a dog chase its tail.

There is used mostly for location. “Put the package over there.”
Their is possessive. “Their car is in the garage.”
They’re is a contraction of they are. “They’re going shopping.”
There’re is a contraction of there are. “There’re ten pins in bowling.”
Just remember: There’re people concerned that they’re risking their lives over there.