I am far from perfect, and I'm not educated. Let me make that disclaimer first. With that out of the way, I've been online for some time and in the last 10 years, it is common to see a few common errors that I'd say we are in danger of introducing into the lexicon via dictionary-squatting:
- it's and its. If you can't substitute it's for "it is/was/has", then you need its, the possessive form of the word.
- there/their/they're
- your/you're
- are/our
- to/two/too - This is the most common, by far.
- definitely - not definately, just say def or something.
I could go on, but it's starting to feel petty or like my standards are too high for personal correspondence. "Elder shakes fist at terminal"