Today transparency is looking, well, odd, it acts transparent in relation with the background, but opaque in relation with itself, it was fine yesterday (sat.).
here one of my models, I can see the background but not the faces behind the front ones.
and here is how it looks today:
here is another from someone else, it's preview shows the faces as they should appear
and a SS from the console:
tried on chrome and FF in Windows 8.1 and on chrome for android