Help Autocorrect woes


I have an issue that is driving me absolutely crazy, and it only happens with my tab, but not my HTC wildfire, which seems a bit weird.
Anyway, i like autocorrect and would like to keep it turned on - but it corrects everything i type into website forms. Every password, email address and name gets "corrected"... I could barely register in the forums here because it helpfully wanted to fix even the captcha.
How can i keep autocorrect on but stop it from correcting website forms? It seems so odd that my Wildfire was fine from the start, but the tab isnt.