What grammatical errors really piss you off?

[paperjam]

[ QUOTE ]
incorrect usage of apostrophe's.

i bet the average person who [censored] this up has an iq 15 points lower, on average, than a person who knows the language.

if i see someone write "book's", i am probably dealing with an idiot. that simple. it is just SO easy, i don't see how on earth someone can [censored] it up. other things like there/their/they're...i don't know they don't bother me so much. although "your a moron" is deliciously ironic.

the other "intelligence indicator" is "should of". only an idiot would ever write that (think that's how it's written).

[/ QUOTE ]

but i could of written that i like the book's cover.