For writings that appear on the Internet, I use three periods for an ellipsis, two dashes for an em dash, etc. I do this because I've experienced the horror of a converter not being able to read smart quotes or common punctuation marks, which has turned my documents into so much unreadable garbage with that strange spade/question mark symbol everywhere. So to maintain readability no matter the format, I leave the auto correct off when I'm writing for the web.