In a CSS file, what is the / for in the font property?

When I see this in CSS:

font:120%/130%

…what's the purpose of the '/' and the two different values? Is this something to do with compatibility between font sizes in Firefox and IE? (Maybe I've just answered my own question, but it's a guess and I'd like a definitive answer - possibly with some pointers to some reference, cos I can't find anything)

Thanks all!

So 120%/130% indicates that the font must be 120% in size, and occupy a vertical space of 130%.

It's shorthand for:

font-size: 120%;

line-height: 130%;