Winners and losers

Dendreon (DNDN, news) plunged to $11.69. The drugmaker withdrew its sales estimates for 2011 and announced job cuts because of lower-than-expected growth in the use of prostate-cancer treatment Provenge. The problem is that the drug costs are extraordinarily high.

DirecTV (DTV, news) fell to $46.63. The largest satellite-TV provider reported first-quarter profit that beat analysts' estimates after gaining subscribers in the U.S. and Latin America.

Sotheby's (BID, news) was off to $39.19. The auction house said second-quarter earnings excluding some items were $1.83 a share, exceeding the $1.57 average analyst estimate.

Transocean (RIG, news) fell to $53.98. The world's largest offshore driller posted its 11th straight quarterly profit decline. Daily rental rates for the company's vessels dropped as much as 26% during the second quarter because of competition from rival operators and an influx of newer rigs onto global drilling markets.

Click here to become a fan of MSN Money on Facebook

Walter Energy (WLT, news) declined to $77.89. The southern Appalachia producer of steelmaking coal reported second-quarter revenue of $766.7 million, missing the $931 million average estimate by analysts in a Bloomberg survey.

Web.com Group (WWWW, news) soared to $10.37. The company that builds websites for small businesses said it is buying Network Solutions and expects the deal to add at least 20% to the consensus estimate of its 2012 earnings.

Zipcar (ZIP, news) rose to $23.23. The car-share company boosted its sales forecast for the full year to at least $240 million. Analysts project revenue of $238 million, according to the average of a Bloomberg survey.

Zumiez (ZUMZ, news) fell to $21.77. The Everett, Wash., retailer reported comparable sales for July that missed analysts' estimates for the first month since December.