The English Major: bad grammar makes me [sic]

over the past year or two, i have had the pleasure of editing and marking some lovely pieces on a wide variety of topics. where there is pleasure, however, there is pain. today, i am wasting my 500th post on the most egregious (hi, Lyris!), and most pervasive grammatical sins i have encountered.

These errors have always been their, its because your stupid.
The following errors are the result of generations of people writing the way they speak.

There/They're/Their
There - the opposite of here. e.g. "She went over there."
They're - equivalent to "they are." e.g. "They're not present."
Their - the 3rd-Person Plural Possessive Determiner. e.g. "The dog was their responsibility."

Its/It's
Its - the 3rd-Person Singular Gender-Neutral Possessive Determiner, as in "Defeating the Russian at the game of chess was its finest moment."
It's - equivalent to "it is." e.g. "It's time to d-d-d-d-duel!"

Your/You're
Your - the 2nd-Person Possessive Determiner. e.g. "You must have lied; your pants are on fire."
You're - equivalent to "you are." e.g. "You're fired."

Comma Splices
I defer to the Wikipedia entry.

The Future Generation of Grammatical Errors
The following have developed in recent years due to the elimination of formal grammar teaching in education. They are intriguing to the descriptive linguists and infuriating to the prescriptive linguists.

'They' is the new 3rd-person singular gender-netural pronoun!

I don't want to tell you who ate the cupcake because they would be mad.

In this politically correct day and age, we no longer default to the masculine for catch-all phrases. Instead of taking the time to say, 'him or her,' or 'he or she,' we now use 'them,' or 'they' as the 3rd-person singular gender-neutral pronoun when referring to people. This shows up quite frequently in anecdotes where the speaker, or writer, tries to preserve the subject's privacy by obfuscating the gender with the incorrect use of 'them' and 'they.'

These pronouns should be reserved for their intended plural usage so that listeners, or readers will know when there are multiple people, or when there is just one person. This error is so widespread, however, that listeners and readers actually have no confusion about the number of people being referenced. Instead, they have adapted to find different contextual clues to inform their interpretations.

Apostrophic Catastrophe's

Buy 20 Hamburger's!

When pluralizing, many people now apostrophize their plurals. It is ridiculous. Things like hamburgers and waiver forms are being anthropomorphized, and given the ability to possess empty space when their sentences are left unfinished. This error is so common that there are now websites to chronicle its infiltration of the unknowing public.

Could of, should of, would of!

"I can't believe they left without me! They could of told me first!"

This one causes me the greatest pain. In fact, I will go so far as to say that I hate this error the most. I don't hate the people that commit this error, but I do hate the error. This is a textbook example of how people craft their sentences based on the way they sound when spoken. "Could/should/would of" makes no syntactical or semantical sense.

Those that commit this crime error want to say "could have," or "should've;" the sound of 've' is very similar to 'of.' Writers must be conscientious of not only how their sentences sound, but how they're read as well.