[html] Expand div to max width when float:left is set

The accepted answer might work, but I don't like the idea of overlapping margins. In HTML5, you would do this with display: flex;. It's a clean solution. Just set the width for one element and flex-grow: 1; for the dynamic element. An edited version of merkuros fiddle: https://jsfiddle.net/EAEKc/1499/