which is the cleanest way of specifying the font-size's unit

[chaits]

Can any1 guide me on which unit to be used for the font-size...like % , em ,px?
and if %, why that only?
if em , why that?.................

please do help me on this..........

thanks in advance.....

[Graft-Creative]

There's a fairly reasonable consensus on setting the overall font size by applying a percentage to the body element, with maybe the line hight specified within the same declaration i.e.

body {font-size: 78%/1.2}

..then using em values to adjust font size on other elements further down the document tree.

Kind regards,

Gary