Great!; It worked fine!
The “empty span” is to justify #main, #sidebar1 and #sidebar2 inside #container. Without the “span” this elements do not fill a line so they do not justify. It´s just a trick!
Check your code pen – the elements are not justified. But if the span is added (and the corresponding CSS), they get justified! http://codepen.io/anon/pen/LrgFz
Do you know another way to do this (justify inline-block elements)?
Thanks a lot,