Do NOT mouse-roll over the black boxes in your twitter stream, as this spreads the madness.
It's a hack exploit that's run a muck on twitter and spams and breaks you page.
3rd party twitter apps are fine however, like tweetdeck and the like - just avoid the main site until the Twitter staff fixes it.
BBC news artical --> http://www.bbc.co.uk/news/technology-11382469