I don't know much about JavaScript but I have a small web application, given to me by a friend, which is used by several companies. Due to the type of application, each company usually requires particular modifications in the UI of specific webpages, basically only in appearance and CSS (not in business rules). In each new installation, I find it tedious to have a different version of the app for each company.

Is there a way, for example for a specific webpage, to have its CSS file outside the application and load it at runtime, without having to compile the application for each company?