Unwanted padding on large monitor (area wich is outside of the grid)

14 hours ago, siba said:

But how to do it in custom CSS? 🙂

You don't need Custom CSS for this, you can change the site width in the styles menu under spacing. You may have to type into the field as the maximum the slider goes to is 3000px. I would say that the wider you make the site width the harder it will be to design your site to look good on all desktops and laptops.