Which language is your native language? If you answered English, then please, for the sake of humanity, SPEAK IT CORRECTLY! If you answered anything other than English (or "American" for you smart alecs out there...), then learn from others' mistakes.
Part of growing up is learning to communicate with other people. Our first communication techniques are simple, laugh, cry, scream, stink. For a year or so, it's cute. After that our parents get tired of us not communicating at a higher level, so we are forced to learn to speak in some form or another. While we are learning to verbally express ourselves, we make mistakes. Those mistakes are cute. "Mommy, I dranked all my melk." Our parents correct us politely and let it go. As we get older, and go to school we learn that you can't just add "-ed" to the end of a word to make it past tense. English is a complicated language and it takes many years to learn, so we take those many years to learn the language.
After 12 years of school, you're a junior in high school. You're around 17 years-old. That means, unless you are deaf (or lived in somewhere that wasn't an English speaking nation), you've been listening to people chatter on in English for 17 years! By this time you should be able to properly (or at least semi-properly) speak with decent grammar. Mormon missionaries live in a foreign nation for two years and come back knowing that native language almost fluently.
Speaking the language is simple enough. You can hear the different fluctuations in people's voices and mimic them. So if you can speak the language, why can't you write it? Writing a paper is a lot like speaking. Of course it's more organized, but that doesn't mean it's harder. I once knew this person who spoke English fluently. We were in the same English class in high school. We would peer review for each other. Every week I was so stunned at how grammatically terrible the essay would be. The punctuation was all over the place, verbs were incorrect and there were so many spelling errors! I just couldn't believe it.
There is no excuse for something like that. Especially when a boy in our class, that wasn't born or raised in America, and only started learning English when he was 12, wrote essays better than our professor. Yes, his essays had mistakes, a sentence error here and there, but for the most part, his essays would have fooled anyone into thinking he was raised by royalty in England. His grammar was impeccable.
If you're over the age of ten, you should know that the sentence "Paco drawed nineteen lemons on a piece of paper." is incorrect. If you're over the age of 12 you should know the difference between "you're" and "your." If you're over the age of 15 and you still don't know which "their," "there" or "they're" to use...please contact a tutor. Once you reach college, you should be able to use proper English in your classes.
Grammar doesn't stop at the edge of campus though. Believe it or not, but scientists have found that 100% of cases on the internet require proper grammar as well. Studies have shown that Facebook, Twitter and basic texting are all times when proper grammar are acceptable!
Updates and posts reflect the person you are. If you constantly post music lyrics, it's safe to assume you enjoy music. If you're always quoting inspirational speakers, then chances are you're a confident person. If you're an Emo Poster, then you come off clingy (see Emo Posting: Don't Do It!). People who use proper grammar come off intelligent sounding. People who don't come off a bit obnoxious and a tad overwhelming.
We may not want to admit it, but social networking has become a major part in our lives. Employers can search for you on facebook, people from all over the nation can stalk you using twitter, and the government can find your cellphone anywhere on the map. How do you want the world to view you? How do you want that cute boy from Science to see you? Do you want a possible employer to look at your status and say "wow, can she even speak English?" Use proper grammar, it solves the problem.
"I've never really been good at spelling, so that is a no-go for me." WRONG! Most internet browsers offer a spell check now. Right click on the misspelled word and options pop up for you. Pick the one that looks closest to what you're trying to spell. (I've done that over a dozen times in this post alone.)
"I'm dyslexic." If this is the case then I'm sorry. You may use grammar however you want.
"Me no speak Engrish." Then please speak your native language.
I can't tell you how frustrating it is to see a post with a word that catches your eye, only to find out it makes absolutely no sense. "Me n Jess flies to France one week!" What?! What about flies and France? By the time I decipher the code, Jess and her friend have already returned from France and I didn't get a chance to ask for a souvenir.
So we can do this the easy way, or the hard way. It's your choice. Anything you say incorrectly can and will be used against you in the Grammar Court (assuming it can be deciphered).