There, it's yours.
Every now and then - usually daily - I get email at work that reads something like:
"Let me know when your back."
And, naturally, I think: "when my back *what*?" before realising that someone I'd previously thought of as highly literate hasn't worked this one out. I'd like to think that this was restricted to those who didn't work in fields that involved lots of communication, either internal or external, but I see it everywhere: engineers, admin staff, senior management. I've seen it in presentations to important customers. I've even seen it in published adverts.
What's hard about this?
"You are". Abbreviates to "you're". Hence has an apostrophe.
"Your" doesn't have an apostrophe. Hence isn't expandable to "you are".
"You're late. Your dog is on time."
And then there is "there". And "their". And "they're".
And "its" versus "it's".
I did look for the "possessive Its FAQ, but it doesn't show up under google, alas. I forget (if I ever knew) who wrote it, but it goes like this:
Q. Does the possessive "its" have an apostrophe?
Q. What, never?
A. No. Never.
And that's it. In its entirety. Current Mood: cranky