When editing text or code it is quite often very useful to jump to the beginning or the end of a line, or to move the cursor one page up or down..
Unfortunately the keys dedicated to this task (home/end/pageup/pagedown on a windows-pc) have got a different meaning on a mac: Page up/down scroll one page up/down – without moving the caret (cursor), home/end move to the beginning/end of a document – also without moving the insertion point.
I’m not sure of which use this strange behaviour might be, to me it’s useless. But fortunately OS X is very consistent and offers the possibility to remap keys globally with a simple XML-file ~/Library/KeyBindings/DefaultKeyBinding.dict.
Further information can be found here: macromates.com
An example .dict-file can be downloaded here: DefaultKeyBinding.dict