Which seems quite new to me as I have never used any percentage values on them before. Took some tests and I found out that all major modern browsers supported percentage values for padding and margin very well, even IE6.
This should come very handy in positioning things up according to the parent width. See how I did with the title of this site: http://www.rackspacepromocode.com
You can resize the browser window to see how there’s always a 8% left padding to the <h1> title.