NEW YORK (AP) ¿ Shares of WebMD Health Corp. traded higher Wednesday after the health Web site operator met Wall Street expectations in the third quarter backed its forecasts for the full year. The company also announced it will start a stock buyback next week. It plans to buy back as many as 5.7 million shares at a premium price of $36 per share. The stock had closed at $34.26 on Tuesday. Late Tuesday, WebMD said its third-quarter profit rose 19 percent to $12.8 million, or 21 cents per share, from $10.8 million, or 18 cents per share. Revenue increased 15 percent to $111.6 million from $96.8 million. Analysts polled by Thomson Reuters expected profit of 19 cents per share and $111.1 million in revenue. Public portal advertising and sponsorship revenue grew 20 percent during the quarter to $89.4 million. WebMD network sites had 59.2 million unique users per month in the third quarter, up 19 percent from a year ago. Total traffic increased 27 percent to 1.4 billion page views.