stylish & mastodon: fixed number of columns

How to have a fixed number of columns visible on your mastodon instance using stylish for Firefox or Chrome (or Chromium):

 

Install Stylish add-on/extension:

Chrome: https://chrome.google.com/webstore/detail/stylish-custom-themes-for/fjnbnpbmkenffdnngjfgmeleoegfcffe
Firefox: https://addons.mozilla.org/en-US/firefox/addon/stylish/

 

Add new style:

Find Stylish ‘manage styles/preferences/settings’ – in Ff’s Add-ons or Chrome’s Extensions. Click “Write a new style”, enter new name for your new style (name of your instance for example), then under “Mozilla format” click “Import”.

paste this into the wide white area (change toot.si into your instance domain):

Click “overwrite style”. Then click “Save” in the left column. You can then edit the number of your columns as desired in this code (see the comment in the code above). Always click save and check the site in the other tab.