How many hidden (from me) mistakes do you think I made in the last question I asked?

While message boarding I find I make a lot of silly typing mistakes and I don’t know why I’m so consistent at it. It’s the kind of thing where I wont even notice a mistake until days after and usually after I’ve re-read and re-read my writing a few times. It’s like mistakes can hide from me for a while until I’m far enough removed from the writing that I can look at it fresh again.

What suggestions do you have for getting a writing technically (grammar/spelling) right the first time you post and avoiding embarrassing errors found days later?