You may have noticed the "alternate stylesheet" while viewing the source code of this website. That's the CSS for dark mode! You may be wondering how to switch to dark mode. It's easy, well at least if you're on desktop Firefox (sorry Chrome and mobile users!).
On Firefox and its forks like Pale Moon and Waterfox, follow these instructions:
Toggle the menu bar (on Pale Moon and SeaMonkey, they are already toggled by default).
Click on "View", or the third item on the menu bar if you're using another language pack.
Hover on "Page Style". (On Konqueror, it's "Use StyleSheet".)
Click on "Dark mode". You can now enjoy my website while taking care of your eyes at night!
For Google Chrome, you will have to install this extension.