Stylesheet not loading

All web pages are looking white with black text, all unformatted. Content present. Everything was working earlier this evening.
Have used different gadgets with cleared out caches and problem still occuring.
Looked at error log but was last modified a week ago.
Backend of OJS 3 looks and works fine.
Saving apprearance again not making a difference.

what did I do last on the dashboard? Upload a replacement favicon and work on a static page. But everyting worked fine after that.
Advice desperately appreciated.

Have you edited the less-files of your theme? It would seem that they are not getting compiled as CSS because the link to your css leads to a blank page:$$$call$$$/page/page/css?name=bootstrap

There could be an error in one of the less files that is preventing them to be compiled.

Or, could be this: Problem with css - #23 by NateWr