What: CSS-Tricks just posted about this last Friday and since I could have used this that day (!) but didn’t find it until now, I’m adding a note here for myself:
You have a page with a table of contents (with links), or you have a one page website with in-page navigation and you have a fixed header — when you click a link the content scrolls up too far and is hidden by the fixed header. This is not a good user experience, and you can improve it with scroll-margin-top in Firefox and Chrome-based browsers…