Are there any practical reasons to use “em” instead of “pt” font size units?

Question

One CSS rule I have learned is that you should use the relative \"em\" font-size unit instead of the absolute \"pt\". The general idea is to set the font-size in your body t

Answer 1

1) IE6 is still widely used and is unable to resize the fonts defined in px. => Usability issues. That alone is a no-no.

2) See CSS Units for example.

3) Most authors agree to say that pt is mostly a print unit: at worst, use them in print stylesheets, where the resize problem disappears...