Sector roundup: Bond, mortgage insurers; Web stocks

Among the sector activity stories for Wednesday, April 23, from AP Financial News:

NEW YORK (AP) _ Shares of bond and mortgage insurers plummeted Wednesday after Ambac Financial Group Inc. reported a steep loss for the first quarter, stirring worries about how badly the credit crisis will crimp the beleaguered industries.

NEW YORK (AP) _ Most major Internet stocks declined Wednesday, with Yahoo Inc.'s shares dipping after the company's first-quarter results came in just ahead of analysts' expectations, but didn't produce many more positive surprises.

NEW YORK (AP) _ Shares of less-than-truckload carriers mostly fell Wednesday, as a Morgan Keegan analyst downgraded YRC Worldwide Inc., saying that a competitor's better-than-expected first-quarter results show that YRC is losing market share.

NEW YORK (AP) _ Shares in Vertex Pharmaceuticals Inc. slid Wednesday while Idenix Pharmaceuticals Inc. gained ground on a mix of study data for the their developing hepatitis C drug candidates.

NEW YORK (AP) _ Airline shares struggled to find footing in a volatile session Wednesday after massive first-quarter losses by Delta and Northwest.