60% wide div in fixed-width (400px) wide div
40% wide div in fixed-width (400px) wide div with a whole bunch of text in it so you can see what it does when the browser window is pulled wide.
60% wide div inside div that's 60% of the browser window
40% wide div with a whole bunch of text in it so you can see what it does when the browser window is pulled wide.
◀ 400px-wide div floated left
60% wide div inside div that's 60% of the browser window
40% wide div with a whole bunch of text in it so you can see what it does when the browser window is pulled wide.
400px-wide div floated right ►
60% wide div inside div that's 60% of the browser window
40% wide div with a whole bunch of text in it so you can see what it does when the browser window is pulled wide.
400px-wide div floated right, clear both ►