By Rex Crum, MarketWatch SAN FRANCISCO (MarketWatch) -- Tech stocks ended the week on a positive note, as several sector leaders advanced Friday, but it was losses from National Semiconductor Corp. and Chinese video-content site Youku.com Inc. that stood out. Investors sold off Youku shares (YOKU), as the company often called China's equivalent of YouTube fell more than 12% to close at $37.50, two days after making its public debut on U.S. markets. Still, since pricing its initial public offering at $12.80, Youku's shares have climbed almost 200%. Another Chinese Internet company that went public Wednesday, E-Commerce China Dangdang Inc. (DANG), rose by 57 cents a share Friday to close at $32.79. Dangdang's shares rallied almost 90% on Wednesday in the debut session after its IPO. The company has been dubbed the Amazon.com (AMZN) of China. Among decliners, National Semiconductor Corp. (NSM) fell almost 8%. Late Thursday, the chip maker reported a 78% increase in its quarterly earnings but gave a weaker-than-expected first-quarter sales forecast. Among leading tech stocks, Netflix Inc. (NFLX) rose $3.58, or almost 2%, to $194.63. Late Thursday, Standard & Poor's had said it would add Netflix to the S&P 500 Index (SPX). Gains also came from Dell Inc. (DELL), Oracle Corp. (ORCL), Motorola Inc. (MOT) and Atmel Corp. (ATML). The Nasdaq Composite Index (RIXF) ended the day up by almost 21 points to close at 2,637. The Philadelphia Semiconductor Index (SOX) also managed to eke out a small gain.