@flodolo Hi Francesco! First of all thanks for this patch! I was taking a look to this, and as now we are moving as well to Tablets, I was considering that moving this `width` to a responsive way could be worthy for the following steps we are doing. 

For implementing this we could update https://github.com/flodolo/gaia/blob/bug977268_ftu/apps/communications/ftu/css/style.css#L497 , adding `width: 100%` and `-moz-box-sizing: border-box` for taking into consideration the padding within the box.

Once we have it, we could add `width: calc(100% - 2rem)` (this is only a suggestion, you can use paddings or whatever you consider it's better), for using all the available space. Wdyt? Thanks!