No, that isn't Twitter. It is Google (English, evidently).

Seriously, this is the weirdest glitch ever. And it seems to happen (and stop happening) at random. I type in the URL, hit enter... and... Hey Google! (Sometimes I am greeted by Yahoo!, just to shake it up a bit). Address bar shows wrong favicon, right URL... and I get Google English. Which I would suppose is not the locality specific UK version...

Done