I am using latest 20-13 theme ;) and I have this problem -- e.g. on page http://fpe.klusik.cz/events/event/kpghrv-nezapomenout-na-korek/ there you can see that events are tooo thin :-)
I tried to use different theme and it was okay, so I think it is 20-13 related.
When I edited CSS it wasn't okay, theme was broken then. When I saved same as original CSS from wordpress edit theme feature (inbuilt), even when I saved unchanged file, theme was destroyed, maybe it didn't save it well, I don't know why that happened.
But my biggest problem is with that events and map, it is not readable at all :-( Thank you ;)