(This is Part 2 of a two-part series on the 10 Dumbest Things on Wall Street in 2010. Click here for the 10 Dumbest Things on Wall Street in 2010, Part 1.)
The FTSE 100 gains more than 1% as oil shares rise.
Leading European oil groups gained more than 5% on Thursday after OPEC's surprise output cut plan. But analysts are unsure the agreement amounts to much.
Energy stocks rise even as oil prices give up initial gains.
The oil cartel will reduce energy output at its next meeting in November, according to reports.