I've had several questions in comments about how to add CSS files using the Simplest-Safest-Most-Future-Proof-Way to customize your SharePoint and SharePoint Online using UserCustomActionConfigPage

This is something I wanted to talk about from day 1 of this series - as I did cover you can add more than 1 CSS files, and specify their ranking via the Sequence number.

Because UserCustomAction doesn't create a link for CSS references, the way to do this is via the ScriptBlock and create a LINK element and attach it on page creation.

How to use this?

Grab the latest configure-page.aspx from Github.

Reference a CSS file instead of a JS file.  The ID is optional, but will be respected if specified.

The Sequence is honoured - 1001 will follow 1000.

Result - the CSS reference is loaded into the page.

Happy branding!