Do you have any idea of how many times I've rediscovered that?

And how long it's taken each time?

That and page-up / page-down. Yes, they're somewhat useful for navigating documents (including webpages).

Regarding page scrolling, I'm usually good with Space and shift-Space.

PgUp/PgDown is useful in some instances, though I'm in OSX rarely enough that I forget what exactly they are when I'm not there.

Terror and repressed memories are like that, you know.

Or ctrl + a in some cases (unixy thing, works in linux terminals as well)

Cmd-Up will also generally bring you to the top of a page.