What is the em font-size unit? How much is it in pixels?

Question

I want to know what the em unit is, and how much 1em is when converted to pixels (px). I also read somewhere about some IE bug, to overcome which b

Answer 1

em is almost the same as percentage, I suggest to read http://kyleschaeffer.com/best-practices/css-font-size-em-vs-px-vs-pt-vs/