I usually use the back space key when I make a mistake. That makes for a post that is easier to read. The more typos and stupid spelling errors we post, the harder it is to get the full value out of it and therefore the less effective it is in dissuading someone from becoming a witless or going to the REJECT Jesus Party next year.
Speaking of spelling errors, does everyone know that the words "lose" and "loose" are two different words? People spell "lose" (as in losing your keys) "loose". That is incorrect--and not just an alternate spelling. It has become very common in the past few years (I never saw that mistake when I was in school). "Loose" means "not tight, not firmly attached, not belonging to a group, etc. To maximize the value of our posts (and in general life), we should start paying attention to those basic spelling errors. Errors in complicated words that are often spelled incorrectly (and the incorrect spelling isn't a wholly different word) are to be expected, but the most common ones that appear in a third-grade spelling book should be corrected as much as we can.
No, I do not expect perfection. Even Simon makes stupid mistakes (and ones that could turn a two second job into a forum outage lasting the morning). Typos do happen, and we do not always catch them all. And some people are confused with alternate spellings and words that are more difficult to spell. But everyone will benefit, ourselves included, if more of us are careful to catch the majority of our typos and fix the third grade spelling problems and errors.