yes the browser does cache the style sheets. I could clear my cache and view a page with a linked css file. This file along with the page will now be in my cache. With a little effort one could figure out what style names go where and then use search/replace and undo any efforts to keep them from being used.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.