>What they use is based on the same principle as I gave you:
>

>.left {
>    float:left;
>    width:120px;
>}
>.right {
>    float:right;
>    width: 100%;
>    margin-right: -120px;
>}
>

>
>Note: this is useless as it's what CSS box layout does by default:
>

>    float:right;
>    width: 100%;
>

>
>Reading this helped me a lot understanding how all this formatting goes; takes less time reading than all the trial and error process you go for finding the right CSS
>
>Back to your problem, I don't think the CSS box model allows what you're looking at; you'll probably will need some JS to do this.

Yes, this is exactly why I was not able to find anyone talking about this.

This can only work if percentage of width is applied.

Yesterday, I added media-screen min-width, so to force it to react for that on one specific device. Other than that, the two columns are side by side, and the right one takes as much space as needed.

Thanks