I'm funny. There are certain words, like definitely, that most folks spell wrong, and it doesn't bother me.
It partly depends on how frequently the word is spelled wrong.

Word substitutions, like: they're/their/there or then/than or whose/who's make me cringe.

One or two words spelled wrong, no problem, but if I have to read a post out loud to understand it, there's a problem. And for several posters, I just don't, it's too annoying to do it over and over again.

I use dictionary.com and webster.com.