I use the dopetrope layout from HTML5up template. Which uses a grid system like Bootstrap.
For example this bootstrap code :
`"class="col-md-6 col-xs-12"`
would be equivalent to :
`class="6u 12u(mobile)"`
in HTML5up. The "u" is the unit of the grid.
I tried to add a column after Xu. With bootstrap we use offset attribute :
`class="col-md-offset-2"`.
EDIT : I just found out it's based on skel.io. I look forward in this direction.
I found the solution in the skel doc.
https://github.com/ajlkn/skel/blob/master/docs/skel-layout.md#offsetting
The solution is -2u for offset columns.