[rtpg]

Global styling done messily can override local styling. It’s the hardest kind of problem to reason about!

I do think that stuff like bootstrap is generally good at avoiding this but it only takes a handful of improperly scoped high level CSS rules to cause awkward hard-to-fix pain much later on.

[skydhash]

Learn how cascading works, then learn how to use the web inspector. I'm using Firefox and the style panel list the the selectors used in order of priority. And you can filter by properties to see which one is overriding everything else (i.e the only one not crossed out).