Ok, I've enabled extensions as you and Markus suggested. Unfortunately the site is still going crazy.
Tech support said it's a cache issue, and there are a couple other problems I've had with Sitefinity that I've been told are related to cache. So I'm starting to think there's something I'm not understanding about cache.
How the heck can cache make a stylesheet completely break, freeze a website, and only on my laptops, but not on desktops running different windows versions?
When making CSS changes, I always use f5 to refresh the CSS, but beyond that, I don't know much about cache. And I don't completely understand the suggestion from support:
Can you try when uploading new stylesheet to: restart web.config/build
the project/whait some time untill the new style document is
addressed/edit the page where the style should be applied and publish
it/clear browser cache.
Sometimes when adding something new to Sitefinity which is web
application project it is not instantly recognized. This is one of the
differences from a website project (Excuse me if you have converted your
SF project to be website, I was not aware.)
restart web.config...what? I've tried opening a page and pubslishing, because I think this clears Sitefinity's cache, but this doesn't seem to be working either. Am I missing something?