Nasdaq says it has modified its system for handling initial public offerings after technical glitches marred the debut of Facebook on Friday.

The delay and other problems in one of the most highly anticipated IPOs in recent years were a setback for Nasdaq, which competes with the New York Stock Exchange in listing stocks.

Facebook was expected to start trading at 11 a.m. Friday but didn't open until 11:32 a.m. Some investors didn't learn for hours whether their orders went through.

The CEO of Nasdaq, Robert Greifeld, said over the weekend he was "humbly embarrassed." It took Nasdaq until 1:50 p.m. to let its members know whether orders to buy or cancel were executed.

Facebook plunged 12 percent to $32.73 Monday, well below its initial offering price of $38.