In the "old" days (back when Jesus was a child; when I was growing up), if someone graduated with a high school diploma, you could trust they could read AND write using correct grammar. Not any more. These things get to me when I see them posted, in messages, on signage (you'd think someone creating the signs could actually proof-read the thing before it's sent out):
To, Too, and Two
Your and You're
Their, There, and They're
Except and Accept
Affect and Effect
Our and Are
When to use "suppose" and "supposed" - as in, "I suppose so" (implying now) and "I was supposed to be..." (implying past tense)
It's and Its
How to make something plural and How to make something possessive; Acronyms, such as DVD, don't become plural with an apostrophe; that's possessive (DVD's vs. DVDs)
I'm sure there's more, but this is enough for now.
What brought this on, you might ask... Today, as I was driving to my doctor's office, I saw an advertisement on a sign for a new day care. KinderLearning...Implies they're going to be doing some preschool stuff. I'm good with that. The sign said, "Is your current day care to expensive?" It's TOO people, not TO! If the person who wrote the sign didn't know the difference, the person creating the sign (it was professionally done) should have proof-read the thing and pointed out the error to the customer. If the person creating the sign couldn't tell the difference of when to use TO and TOO, then that person shouldn't be making signs to sell to people.
Several years ago (20+ years), the company I worked for was closing our main office and only having agent offices. We ordered a sign from a well-known Wichita sign company with the address of the new agents. The sign maker abbreviated Kansas with KA - not KS. It wasn't a typo because it was done more than once. If that had been the only error, I might have bought into typo; it was so poorly done and the spelling was so bad, we refused to pay for it and had the owner of the company come and look at it. He stood there for a minute reading the sign, and then he picked it up and left our office without saying a word. We didn't get a bill.
OK, I'm off my soap box now and back to regularly scheduled programming.