I wonder what they teach in schools today. In the Rules and Guidelines of a well-known webbased forum I read:

3. If you’re English is not perfect, no problem but than always try to make short understandable sentences

That’s such bad advice it’s not even funny! It’s “your English”, the comma is in a strange place, I’m missing a dot, and your English should at least show some attempt at making it understandable, i.e. it is a problem if it’s not perfect. Let me put down some simple basic rules:

You’re – A contraction for “you are” (You’re hot!).
Your – Ownership (Isn’t that your car?).

They’re – A contraction for “they are” (They’re leaving now).
Their – Ownership (That’s their car).
There – A place (It’s not here, so it must be over there.).

Our – Ownership (That’s our car).
Are – Are you really that dumb?

Two – The number 2.
Too – “Also” (I want some too) or “in excess” (That’s too loud).
To – All the other uses.

Breathe – Verb, action, pronounced BrEEthe (I can’t breathe).
Breath – Noun, a thing, pronounced Brehth (Take my breath away).

Than is a conjunction used in comparisons, like: Julius is smarter than you are. This is more important than you might think. Is he taller than me?

Then has numerous meanings.
1. At that point in time; I wasn’t ready then. Will you be home at noon? I’ll call you then.
2. Next, afterward; I went to the store, and then to the bank. Do your homework and then go to bed.
3. In addition, also, on top of that; He told me he was leaving, and then that I owed him money. It cost $5,000, and then there’s tax too.
4. In that case, therefore (often with “if”); If you want to go, then you’ll have to finish your homework. I’m hungry! Then you should eat.

The Bottom Line:
Than is used only in comparisons, so if you’re comparing things use than. If not, then you have to use then. How hard can it be?

“I would of thought that”
is getting more popular by the day. “of” is not a verb. It should be:
“I would have thought that” !

Then, of course, there are idiots writing “it’s” when it should be “its”.
it’s is from “it is” or “ït has”, and
its is (once again) for ownership; Its own mistake, for the computer-software making its own mistakes.

And there is a growing number of fools using “sports” where they mean “supports”;

to sport = to amuse oneself, to play, to mock or tease, treat lightly, toy with (“Robin sports with her emotions”). Also; to wear (something) with pride, i.e. “Brenda’s sporting a new pair of shoes.”

to support is mistakenly replaced by “to sport” when used in this meaning: To provide materials, effort, information or endorsement for a specific activity, ideal, or entity. As in “This new camera supports the micro four-thirds format.” or “This audio software supports several outputs at once.”

Hope you learn a little from this! Honestly, you should be ashamed that I, being of Dutch descent (my father was born in Voorburg, my mother in Utrecht), make fewer English mistakes than the average person I see writing in his/her mother language! English is easier to learn than Dutch, the rules are more logical and straight forward, so there’s really no excuse for the mistakes I mentioned above. You can always use the online Merriam Webster or Googlefight if you’re not sure about something. Also check this cool site about Apostroph Abuse, it’s a hoot!

[ Update 2010: I noticed that TheOatmeal has done something similar to the above. ]