I have received " I cannot except (smoking/pets/etc)...." in RC's so many times, I thought I would post this from vocabulary,com:

accept/except

To accept is to receive, and except is to exclude, usually. Both are busy little words skipping around to different meanings, but they never run into each other.

To accept is to receive something like tea, an idea, or a student into your college:

He accepted tea from Annette without looking at her. (Mary Cholmondeley)

Comments are accepted for a month before guidance is adopted. (Seattle Times)

Mary J. Blige Says She's Been Accepted To Howard University, Howard Disagrees (Huffington Post)

It's difficult to find accept used incorrectly. Score one for English speakers! It's accept's nemesis, except, that poses problems. Except usually means "unless" or "excluding," but it's sometimes used as verb "to leave out." Read all the examples below except the ones you don't like:

He defined solitary confinement as an inmate being held in isolation from all except guards for at least 22 hours a day. (Reuters)

Quiet, benign, his gestures small but eloquent, he barely talks except about the music. (New York Times)

But thickness excepted, he made about the same figure in the street next day. (Bjørnstjerne Bjørnson)

It's the verb form that confuses, and it's usually except when accept is wanted. So remember: to accept is to receive or believe something, but to except is to leave out. Accept something by giving it an A, or exclude it with a big fat X for except.

So, please check your RC's if you won't  ACCEPT certain things for whatever reasons......

Many people also don't seem to know the difference between advice and advise. That one always annoys me. You are not asking for advise, people!

And don't get me started on affect and effect.

I think the most common mistake I see is there and their.

I have some trouble with affect and effect. I always have to think about that before a use one of those.

While on the subject of grammar pet peeves, let me add my 2 (cents):

People who confuse your and you're.

The phrase is should have and not should of.  Similar deal with could.  And would. To contract that phrase, use should've.  Or could've. Or would've.

Writing "your" for "you're" is also one of my pet peeves, as well as confusing "should of" for  "should have" or "should've".

Two other phrases I find annoying are "try and do something" rather than "try to do something", and "all kinds of things" rather than "many kinds of things".

Using "  I could care less" instead of " I couldn't care less".

Mine?  Loose and lose.

The one that I fail to see how anyone could confuse is then and than. But they do.

sole for soul (just read that one today somewhere here in PBS land) 

ben for been  

I'se for - I don't know what - I'm assuming it was for "I have...", but I'se never ben sure.

When I am writing I do not make grammar mistakes. But when I am typing, my fingers often hit the keys they want to hit, not the ones I want them to hit. For example, I just noticed my fingers spelled 'grammar' with an 'e', as in 'grammer,' so I had to go back and correct it. They also like to spell 'then' when I want to type 'than', and vice-versa. And they often add a 'that' to a sentence when it is not necessary: for example, "the keys that they want," instead of just "the keys they want." 

I have discussed these errors with them so many times, I have given up. Now I just go back and read what they type in the hope I catch their deliberate errors and then can correct them.

What often surprises me about other people's writing is their refusal to use commas.

I work in a lab and have seen things marked "poisoness" instead of "poisonous".

Using "how come" instead of "why".

I'm also in the "there," "their," and "they're" camp; and the "your" and "you're" camp; and the "past" and "passed" camp; and most others mentioned here.  

I have a friend I exchange emails with frequently who makes all these errors and plenty more and I love the guy but I always cringe when I read his emails because they're just chockablock full of these grammatical and homophonic errors and he held a moderately senior level gov't job that required a fair bit of writing.  My favorite, though, is when he writes he's going to take a nap on the coach.  He gives a figurative rolling of the eyes when I ask if the coach took him anywhere interesting during his nap or if his coach comes equipped with a couch but he keeps writing "coach." 

Ain't et wunderful! 

The American language is sumting else - it has progreesed (devolved?) into it's own form of communication. It's called the English language but at this point in time it seems it has taken a life of its own. I like to think that the american form of English has progressed (devolved?) into its own peculiar form of communication and has done so by assimilation of so many, many, many other languages into a modern collection of words and phrases that the English language (not American) has somehow failed to add to the collective. It has in essence become Americanized.

I'm amazed when I read/hear other languages being spoken, or seen that drone on and on in their particulat languages and then as you hear or 'see', the american words will 'come out' as the 'local laungage' has no words available that convey the same meaning or ideals. Think Hamburger, or Aircraft Carrier, or Big Mac - words that flow in Japanese until they get to certain words which are American (or English). Same for Spanish words (or Mexican, which I also believe is different from proper Spanish).. Communication is a wonderful experience between so many cultures, but the true wonder is when we bypass the strict rules of our own languages and just let the new words flow as they may...eventually they 'find' the place where they belong - stuffed shirts can go to heck (well - you know what I mean).

I like reading what people mean to say (and as they say it) - there's nothing worse thnt a stuffed shirt saying everything all nice and propwr when you really just want to 'say things' as the folks on the street really talk/ There's a time and place for everything - and sometimes everthing has nothing to do with being proper. How boring would that be ? ? ?

Yowza - life is grand, and down with being proper all the time. 
Sometimes ya gotta stick it to the 'man! - just for funz and gigggles - (yes, there's 3 g's togeter here - 4 in total - why not?)

.

There's the 'proper' grammatical expression as well as the improper grammitical expression - I occasionally like to write as people speak - 

I guess because I took 5 years of Latin many moons ago, it really bothers me when people write ect. instead of etc. To me ect is electroconvulsive therapy.  Also bugs me when people are confused about whether to use e.g. or i.e.