Damn. The front page of HN for this ? Oh, the Erlang days of glory past, I yearn you so much.
Getting elements to align nicely in CSS is a real pain point for a lot of developers. The popularity of layout frameworks is also evidence of that. It's not trivial to take a design from balsamiq or photoshop and replicate it in CSS. Tricks such as this can make it a lot easier to do with CSS rather than relying on javascript tweaks.
I've seen functions attached to window.resize which are principally there to resize a whole bunch of elements dynamically so they still fit together well on a new layout.