Three columns

With this: Lightweight Grid Columns

That's the one, thanks David! :)

How do I get the three columns occupy 100% of the page and displays properly on all devices?
http://gustavosamorano.com/estilodevida/

To make the columns 100% width of your website, set the "Inner Box Type" in your section to "Fluid".

The plugin allows you to choose the width of your columns on desktop, tablet and mobile, so it depends on your preference.

For three columns, I would suggest grid-33 on desktop and tablet, and then grid-100 on mobile.

Ok Tom, I'll try it,
Thanks!

No problem! :)