pixels and em's (1 Viewer)

[rourkey]

I've just been nosey-ing at someones css and his sizes are in em and not pixels
could somebody please explain what em's are and tell me the conversion rate into pixels.
i would be most grateful.
Thankyou!

 

[Minkey]

em is the actual font size, theoretically this is the proper way but most people use pixels.

Explination [quote="W3C specs]one em is equal to the current font size of the current element[/quote]

More info