It only takes a few seconds to re-read your posts. Youre using a computer, you have a plethora of information at your fingertips. One can easily look up the spelling of words, and a few seconds of checking your post will clear up any problems, if you dont want to get Firefox.
Firefox is an excellent option if you would like a word check. Or just read through what you are saying before you post something. A lot of people on this site have bad spelling, which could just be fixed by getting a better browser.