What was that again?
I don't know if this happens to any of you, but I'll be browsing along, happily, and then I'll think, "Oh, I haven't checked such and such. I should do that, right after I finish with the page I'm on." And then when I finish with the page I'm on, all I'm left with is a memory of there was something else I wanted to check; I just don't remember what it was.
The other thing that drives me nuts is I can never remember if I've locked my front door or not. Literally, two seconds after leaving my apartment, I stop and think about it and every now and then, I will actually turn around, check it and it's always locked; I just can never remember locking it. Granted, it's one of those unconcious activities, and possibly not as dangerous as driving somewhere and not remembering how you got there, but still.
Now to remember where I wanted to go...