Sometimes when i'm accessing fhem from the internet it doesn't load the stylesheet. When i inspect the page i get a 503 when trying to load the /pgm2/style.css. It seem to be very random but when it starts doing it seems to persist until i come back to it later. For info i use chrome to access from work. Any ideas??
There must be a proxy/etc between FHEM and your client, which generates this error.
FHEMWEB (the Webserver inside FHEM) has no idea about the HTTP code 503.