seir's post in Maxthon showing only plain text was marked as the answer
Okay, I found the fix. First of all, that issue was visible only in Ultra mode. I found that turning to Retro mode shows websites as it should.
I turned off AdBlock Plus and it fixed the issue. I also found that pages I've tried to run were whitelisted. When I turned ABP back again it was still okay so looks like restart did the fix.