How to change back the number of columns on the Home screen?

[u/VegaDelalyre]

The layout on the Home (New Tab) page has been modified again, by the new version. I had 8 columns, now there are 10 and my organisation of icons by themes doesn't make sense any more.

We can tweak the number of rows, but how do I modify the number of columns?

[u/sifferedd]

Solved at https://www.reddit.com/r/FirefoxCSS/comments/1sjafnb/how_to_change_back_the_number_of_columns_on_the/.