Today I noticed my website http://mint-nachhilfe.ch/ was down, but other people (located in different networks) said it looks up from there. When I came home, I double-checked, and I can really reach it from here. Also, this website considers it down.
Some facts:
It's a Tomcat webapp, connected to an Apache2 server. I restarted both, no change.
Another (ruby on rails) application is connected to this Apache2, which I couldn't reach either, but is considered online by above check website.
At any point, I could directly connect to the Tomcat over http://mint-nachhilfe.ch:8080!
I don't know how to go on searching for the root error. I assume it's related to the Apache2 server, but how could that be?