What does 16px/28px mean in a css font rule?

Question

I keep on seeing font styles like font: 16px/28px 'Open Sans', 'Helvetica', sans-serif; and I just can't find out what the 16px/28px could mean. Why are there two different font sizes defined?

Answer 1

It sets both the font size and the line height.

See MDN documentation's example :

/*Set the font size to 12px and the line height to 14px. Set the font family to sans-serif */

p { font: 12px/14px sans-serif }

Answer 2

16px/28px = Font-size and line height respectively

http://www.w3.org/TR/CSS2/fonts.html#font-shorthand