I promise this won't turn into a grammar blog, but I'm going to sneak this one in.
The plural of typo is typos. It is not typo's. Repeat: TYPOS. This is a fairly straightforward example of adding an -s to the end of a singular noun to make it into a plural noun. Like radios. Zoos. Halos.
Anyway, I don't really care that much when people make plurals with -'s. Most of the time, honestly, I think it's a mistake, and if you showed them the word and said "What's the plural of this? How is it spelled?" they would know. But with typo, this mistake is just embarrassing. Because it's a typo on the word "typo." And you see it in the funniest places.
"Our agency will then hire a professional editor to check your work for mistakes and typo's."
"I hate self-published books because they're always full of typo's, and they're badly formatted, too."
"Please be sure that you have checked for typo's before you submit your work to us, or it may be rejected."
See how that just totally destroys your credibility? Yeah.