Shares of Facebook (Nasdaq: FB), the No. 1 social networking site, fell nearly 2 percent on Thursday, exactly three weeks after the company took in $16 billion in its initial public offering.

Facebook shares closed down 50 cents at $26.31, only slightly above their daily low of $26.15. On Wednesday, they set a record low of $25.52.

No new analyst recommendations were published for the Menlo Park, Calif.-based website that claims 901 million members. On Wednesday, Nasdaq OMX Group (Nasdaq: NDAQ) announced a $40 million compensation fund to handle problems that arose when the computerized exchange's computers froze when Facebook shares first started trading on May 18.

On Thursday, Knight Capital Group (NYSE: KCG), estimated its losses from the freeze could exceed $200 million compared with a prior estimate of only $20 million to $30 million.

Facebook shares have now lost nearly 31 percent of their value. The company's value is $56.3 billion, down $47.7 billion in three weeks.