in my school, lecturers post their lectures online so that we can d/l them, print a copy and read up before the lect. sometimes you get lects which are filled with subtitles of the reference books. sometimes, the pictures from those ref books. and just sometimes, a bloody 265MB whopper of a (*&(!$^"$% file that after 15 min of painstaking d/ling you discover to your horror that you cannot open because it is so damn large your com hangs.