Huge day for stocks - Dow soars almost 500 points

This was one of those all-good news days - starting with word this morning that central banks around the world will work together to stem the European debt crisis, or at least they'll try. Also came news of China loosening its monetary policy so that banks could increase lending activity. And private-business hiring in the U.S. rose by 206,000 in November, the largest monthly gain this year. It's easy to poke holes into all of these developments as too little or unreliable (the fact that the central banks took this action could point to how critical the debt situation has become). But much of the market is built on psychology, and so today's big move could put investors in a happier mood - happier, as in spending more money during the holidays. Also keep in mind that markets tend to turn when the mood is at its bleakest, and it was pretty bleak just a couple of weeks back. Final scorecard: Dow is up 490 points, or 4.2 percent, to 12,045. Not to put a damper on today's session, but the government employment report comes out Friday morning, and investors could turn sour if the numbers are at all disappointing. The main point: Stocks remain extremely volatile and could swing very quickly.