Based on the source in the page you referenced you have a few things going on:
- Your site is assigned a stylesheet in the Sites app.
- You site code name (procaps) is the same as a directory under
/App_Themes (/App_Themes/procaps) therefore IIS automatically delivers any CSS files automatically. THIS IS NOT A Kentico issue, it's how IIS functions.
- You have references manually added to the master page which look they are duplicated
Start by removing all references and find out what is added automatically and what isn't.
If you want to manually add references to your site, remove the reference in the Sites application to your stylesheet. In the Sites application edit the specific site and set the site stylesheet to none.
Next go to the Pages app in the content tree and select the master page. After the page loads, select the Master Page tab. Verify your <head> tag references in there. I'm willing to bet you find some stylesheet references in there, remove them.
Now check the design tab of the page template. Look for any grey webparts which would be HEAD HTML webparts. They may have references to CSS in them. Set the visibility to not display.
Clear the cache on your site, log out and reload the page. What CSS files load? I'm willing to bet any files in the /App_Themes/procaps directory are showing in your <head> tag. The solution to fixing these "automatic" loading files, is to move them to a different directory. We typically put them in the site specific directory, yours may be /procaps. This way you have complete control as to when they load and what to load.
What I'd do now is:
- Not assign a stylesheet in the Sites appliction
- Move your files out of the
/App_Themes/procaps directory
- Add a HEAD HTML webpart to the master page and add all your stylesheet references in there. This will be the safest solution to being able to control what is loaded, where it's loaded and when it's loaded.