Well, this is in addition to my other question (Flickering windows and menus - Ubuntu 16.04). At the moment I am forced to run Mozilla through a terminal, which made me notice this popping up in it:
[Parent 2851, Gecko_IOThread] WARNING: pipe error (119): Connection reset by peer: file /build/firefox-itlqqH/firefox-57.0.4+build1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 353
ATTENTION: default value of option force_s3tc_enable overridden by environment.
I have no idea what this means and googling it has not been helpful in the slightest. I am running Ubuntu 16.04 LTS and I just installed it the other day. As far as I can tell, Mozilla hasn't been affected by this error as far as I can tell, but I also thought Ubuntu was running fine so I just want to make sure this isn't going to cause more problems later on.
