No, it's completely incorrect. In fact, it's annoying to see so many people learning English but blatantly disregarding the rules of the written language. While we're on this subject, sentences should also start with a capital letter, and languages (French, English, Urdu) and countries (Russia, Japan, Mozambique) should too! Rant over!

Some people think the writer who uses "i" for "I" is lazy or non very competent in basic English. (It is, after all, a rule from any beginning English class.) In any case, a lot of people will judge the writing as "poor" even before they look at the ideas in the writing, which is sort of unfair because the rest of the grammar and content could be very good.

Never correct. Never ever. "I" is a pronoun, and commonly used. "i" means nothing by itself - just a lost letter of the alphabet.

I is correct =)

"I" is correct, and all sentences should begin with a capital letter too. After a punctuation mark, there needs to be a space. But online, English speakers often break the rules, out of laziness or just because it's faster: "hi how r u, im good. i like pizza." I think when you're learning English, you should write properly though!