Updated from 1:05 p.m. EDTInternet stalwarts eBay ( EBAY), Amazon ( AMZN) and Yahoo! ( YHOO) powered through their 52-week highs Tuesday as a combination of money manager greed and short-seller fear produced decisive upward pressure. In a sign of how potent the post-Iraq war rally has become, eBay's intraday surge through the $100 barrier for the second time this month left the stock at levels last seen in March 2000 -- the month the stock market bubble burst. By the 4 p.m. EDT close, eBay had gained $3.61, or 3.6%, to $103.05. Yahoo! tacked on $1.48, or 5.2%, to $29.97, while Amazon was up $2.13, or 6.5%, to $34.85. "There is some short-covering and some institutional buying; we're seeing a combo of both," says Jack Francis, co-head of equity trading at UBS. "Clearly people are nervous about their shorts. The volume isn't really, really robust but nonetheless it's decent." But he and others are skeptical that the rally can be sustained. "The question of fundamentals will come into play. Right now, the market seems to be ignoring it, because fundamentals certainly don't support the prices." Lately, plenty of anxious money managers have been chasing the recent hot stock performance, says Vincent Colicchio, co-manager of the ( GBTFX) All-American Equity fund. "If you look at the S&P tech components, the Net category has been the best-performing. So money managers don't want to lose performance and they're chasing them. But we've avoided them because we think they're overextended." As of Friday's close, TheStreet.com Internet Index had jumped 32.2% year to date, far overshooting the Nasdaq's rise of 13.1%. To be sure, Colicchio gives the Internet retail group credit for improving fundamentals. "It's becoming clear there's a real value there. The Internet retailers last year ... actually broke even financially, so that's a seminal event. And Yahoo's doing a good job of diversifying away from advertising, so things are moving in the right direction. But that doesn't mean they're not overvalued."