This perplexed me for quite a while when I first started using Powerpoint and
its not clear from the help files either. The answer is that everything on
the slide master repeats in subsequent slides so you can put anything in the
slide master and it will repeat (until you use another slide master). If
the thing you put in is at the top, then you could properly call it a
"header". The confusion arises because there is no set position in the slide
master for the "header" whereas there is for "footer". So you think, "I've
can put in a footer but I can't put in a header". This confusion is
compounded by the "header and footer" item in the view menu. Clicking this,
you confidentally think you will be able to view the header and footer entry
for slides. But all that appears is the footer entry for slides! Er .. am I
doing something wrong?
Having said that, I think pp is brilliant.