I started doing a good bunch of minor updates to the website yesterday with the result that one of the updated components contained a small bug.
That resulted in an issue that blocked the Portals main menu and its sub-menus.
If your first thought was "whats wrong with my stupid browser today?" - > nope that wasn't the issue.
I meanwhile found a solution to the problem and everything should be working fine again.
However, if you still encounter issues you can report them here.