Two prominent media companies made successful debuts on the New York Stock Exchange on Wednesday, one giving hope to private equity firms looking to clear their books and one fueling talk of a new Web bubble.

Shares of Nielsen Holdings , the consumer measurement firm known for its dominance in television ratings, were at $25.53, 11 percent above their $23 initial public offering price in afternoon trading.

Meanwhile, shares of online media company Demand Media Inc were trading at $22.98, or 35.2 percent above their $17 IPO price.

Nielsen raised $1.6 billion, nearly a tenth more than expected. Demand Media, an online company that relies on an army of freelance writers to churn out articles and video designed to appear at the top of Web searches, raised $151.3 million, more than a third above its target.

Nielsen's capital raise is the first of what is expected to be a rush of big private equity-backed IPOs in 2011.

Its performance could set a positive tone for other buyout-backed IPO candidates, including retailer Toys R Us , hospital operator HCA and pipeline company Kinder Morgan.

Nielsen was taken private in 2006 in a deal worth just over $10 billion by private equity firms Carlyle Group , Blackstone Group LP , Kohlberg Kravis Roberts & Co , Thomas H. Lee Partners, AlpInvest Partners and Hellman & Friedman.

Nielsen sold 71.4 million shares, representing about 20 percent of the company. At the stock's midday price Wednesday that valued the company at just over $9 billion.

The Demand Media offering, while much smaller, was seen as something of an icebreaker for more and larger Internet-related deals this year, like group discount site Groupon, business network LinkedIn and social games company Zynga.

Underwriters on the Nielsen IPO were led by JPMorgan and Morgan Stanley, while Goldman Sachs and Morgan Stanley led the underwriters on the Demand Media IPO.

(Reporting by Clare Baldwin and Jennifer Saba, editing by Gerald E. McCormick, Derek Caney and Matthew Lewis)