Multisite pages broken – not loading css?


I’m setting up my first multisite, but I’m running into problems with the first (and probably all) site I’m creating.

The main site is fine ( But whenever I create a new site and set up a very simple homepage in the same style, it turns out the site’s stylesheet or whatever it may be is broken and all of a sudden it looks like this:

It should look the main page. I’m using the same elements and CSS.

Any ideas? I’ve tried setting up another site within the network to see what happens, but it’s the same.