Page Not Found Old CSS References Recently, we did a complete overhaul of our theme. We have been working with a subtheme of Zen. We are still working with one, but we made it from scratch. Though it is now in place, we are receiving "Page Not Found" errors with calls to the old css files. Has anyone experienced this before, where could they be getting called from?

I've checked to make sure no css file is importing them and no info file is calling them.
You should do a search of the entire codebase (not just theme files), as well as a database search in all tables (it should only take about 3 minutes).

UPDATE:

Also, make sure you have taken any content delivery network (CDN) caching into account. Are these files causing "File-not-found" errors from a remote browser, or from a browser on the local machine (dev laptop, for instance).

If you do have a CDN in place (MaxCDN, CloudFront, Akamai, etc.) you can try uploading a mostly blank CSS file with the same name as the one that you're attempting to get rid of.