Ohhhh boy do I have a lot of these that bug me! Including the ones that have been mentioned already!
I hate when people write to instead of too!
I also hate improper apostrophes or none at all. "I have a lot of cat's" "My cats walking down the stairs" and it seems that hardly anybody understands a possession with a plural word. If you have two parents, you are not going to your parent's house, you are going to your parents' house.
I knew a guy I talked to online a lot, but had never met in person (my cousin's ex - my cousin and I are best friends but we live far apart!) Anyways, his grammar and spelling were absolutely AWFUL. I had to think about and decipher what he was trying to say. I told my cousin later after meeting him in person that I was actually blown away by how eloquent he was in real life. It was like he was a totally different person than the one I had in my head!
And that brings me to being glad I met my husband in real life before seeing him write or type
I am trying so hard to hold back and not correct him so much anymore. But it bothers the heck out of me when he writes "will" instead of "we'll" or "we will" I ask him a question and he responds with "will see" and I rip my hair out
I have a friend who has been looking for a job for a month, and she doesn't understand the importance of good grammar and spelling in a cover letter. They are just awful
She sent me one at work asking if she had all the content she needed. I said yes, but I told her I will edit it on my lunch break for her... She just said "no that's okay I just want to send it off asap" It had spelling mistakes and the name of the company was not even capitalized. She has sent out at least 20 or 30 resumes and has not even had a call back.