I give people the benefit of the doubt - some of them are trying to post using their little phone keyboards, and for some English is clearly their second language - gotta give 'em points for trying! OTOH - I'm a bit judgmental of websites that have a lot of grammatical errors - don't they know what "proofread" means?! It looks very unprofessional, careless.
My pet peeves - there/their; then/than; were/where - but I consistently misspell a few words myself and have to go back and correct them. Brains are funny things... so I'm not too hard on others, lol.
Saw a funny t-shirt the other day that you'd like, UUN - "I'm correcting your grammar as you speak." LOL
~W