I have seen many comments on different blogs and forums where English native speakers spelled you're as your. I'm not a native speaker, but I know and understand the difference between the two. Why is there a confusion?
My initial guess is that your and you're have similar pronunciation and because I carry some accent from my native language (Romanian) I can identify the difference better.
Edit (thanks Chris): The same can be asked for other homophones: there/their/they're, its/it's.
The answer is simple.
You just need to think about how you learned your native language. By ear.
Children learn how to speak their native tongue first, and only then learned the grammar and spelling. Thus, many will "sound" a word out to spell it.
English language learners, on the other hand, usually learned how to spell a word first, and focused on pronunciation later.
I think that the same goes for all languages. Native speakers that do not take the time to learn their own language properly, or that do not read much, tend to misspell homophones.
In French, for instance, many people will replace infinitive form (« manger », to eat) with past participle (« mangé », eaten), or confuse « ses » and « ces » (his,her vs these).
Astonishingly enough, foreigners that study the language do not have this homophony problem in their “source language” and therefore are aware of a grammatical difference. It sounds like people assume translation is mathematically speaking an injective thing.
The confusion is that in many UK (and probably US) schools the difference is not taught. The use of the apostrophe is considered by many to be totally confusing and so it is omitted in many places where it is required.
There is a name for the addition of extra apostrophes in places where they are not needed. These are "Grocers' Apostrophes" which refers to the common sight on market stalls and grocers' shops where the price labels may erroneously refer to "Banana's" or Apple's".
Sometimes I wonder how often this mistake is made out of carelessness, versus ignorance. I'm well-versed in the difference betweent the two, yet I've still made the gaffe on occasion.
Due to the homophoneous nature of the words, the mistake is easily made while typing, and particularly easy to miss while proofreading, too.
In American English (I can't speak for other varieties), even though the two are both spelled and pronounced distinctly in standard writing and slower articulate speech respectively, they tend to be pronounced the same in regular speech.
you're = \yər, ˈyu̇r, ˈyȯr, ˌyü-ər\
and
your = \yər, ˈyu̇r, ˈyȯr\
(from Merriam-Webster, with American rhotic pronunciation). Note that the only difference is the one variant for "you're".
So it is understandable that there is the possibility of mistaking one for the other. This pair, like other homophones are often mentioned explicitly in language studies in elementary school in the US. Making the mistake later in life is usually simply a one time mistake (like the other homophones). If the mistake is systematic then that is probably a sign of lack of concern for orthography.
I think people get confused because the apostrophe is used in possessives as well as contractions, but in this case the possessive your has no apostrophe.
Not an answer as such, but I'm sure this might help some people: http://yourandyoure.com/ :)
