It looks like the stylesheet loaded from javascript (or maybe iframe - if exists).

To reproduce the source loaded, you can do the following:

1. Open Inspector > Network
2. Click Filter Box and type example.com (or what ever the problem url error occured)
3. Force Reload the page (ctrl + shift + r)
4. Select the filtered with url example.com, click / select, and the right section will appear, and then select the initiator.

You could find what caused css to loaded as is and trace it