Chapter 3. Change CSS
You can customize the look and feel of the entire Developer Portal to match your own branding. A standard CSS stylesheet is available to provide an easy starting point for your customizations.
In this tutorial, you’ll add your own CSS customizations to your Developer Portal and reload it to put your new styling changes live.
3.1. Step 1: Create a new CSS file
There is a default stylesheet, default.css. It is quite large and complex, so rather than extend it, it’s better to create your own stylesheet for any of your own customizations to overwrite the defaults. You create a new stylesheet the same way you create a page (just remember to choose an appropriate MIME content type in the advanced page settings).
It’s important that the selected layout is blank. Otherwise the page layout HTML will obscure the CSS rules.