Facebook Inc. and Yelp Inc. are set to lead the biggest year for U.S. initial public offerings (IPOs) by Internet companies since 1999, Bloomberg reported.

Facebook is considering the largest Internet IPO on record, and regulatory filings show that at least 14 other Web-related companies are planning sales. The industry may raise $11 billion next year, according to data compiled by Bloomberg.

That would be the most since $18.5 billion of IPOs in 1999.

Surging sales growth may lure investors to Facebook, the largest social networking site. However, heightened stock volatility and Europe’s sovereign-debt crises could slow the pace of global IPOs after a 38 percent decline in 2011.

Even Internet companies may cut valuations for their offerings after Zynga Inc. and Pandora Media Inc. slumped following share sales this year, according to researcher Morningstar Inc.