Layout, the Final Frontier

The following example will result in
a 25%/75% split on small devices,
a 50%/50% split on medium devices,
a 33%/66% split on large devices.
On extra small devices, it will automatically stack (100%).

Resize the browser window to see the effect.

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Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo.