Hi people!

I have started to learn html&css and now this dilemma troubles me: em or %?

My web is responsive but I'm not quite sure.
Footer is ok when I maximize but body and header are strange. Hm.

Are those dimensions ok or not?
body {position:absolute;width:auto;max-width:100em;min-width:10em;height:50em;top:0.5em;margin:auto;left:0em;right:0em;}

Pleas, give me direction. I'm trying to make simple web page for hairdresser.

Sorry for bad English.