The iShares Dow Jones Transportation Index ( IYT) exchange-traded fund was one of Friday's best performers. Holding CSX ( CSX) rose 3.5% after the company's chief executive said the company should have a stronger second half of 2007. The ETF was higher by $1.26, or 1.4%, to $88.93. Also among winners, the PowerShares Lux Nanotech ( PXN) ETF rose as holdings Arrowhead Research ( ARWR) and Cambridge Display Technology ( OLED) were rising by more than 4%. The ETF was higher by 21 cents, or 1.2%, to $17.48. On the other hand, the Biotech HOLDRs ( BBH) ETF was sinking. Holding Genentech ( DNA) said first-quarter revenue will be unchanged from the fourth quarter, and the stock was falling 3.9%. Meanwhile, Amgen ( AMGN) was down 3.9% on word it would stop work on a colon cancer trial involving its drug Vectibix in combination with other medications. The Biotech HOLDRs was losing $4.19, or 2.3%, to $177.64. ETFs tracking metals and mining were also declining. Gold slid $6.90 to close at $657.30 an ounce, and silver lost 25 cents to $13.23 an ounce. The iShares Silver Trust ( SLV) slumped 1.9% to $131.32. The iShares COMEX Gold Trust ( IAU) ETF was giving back 0.9% to $65.24. The streetTRACKS Gold Shares ( GLD) ETF was falling 0.9% to $65.15. The Market Vectors Gold Miners ( GDX) ETF was recently down 0.9% to $39.61.