In Volatile Market, Google Dominance Never A Sure Thing; Yahoo, Microsoft Loom Large; Google's lead impressive, but search engine field is no stranger to shakeups.(A)

Byline: PETE BARLAS

Google is king of search today, but tomorrow?

No one can answer that, but some interesting points emerged Thursday when the company filed for its initial public offering.

One point is that Google has a huge lead in search ad revenue. Another is that the two founders and chief executive vow to take a long-term view, even at the expense of short-term gains. A third is that it concedes to facing "significant" competition from Microsoft and Yahoo.

And Microsoft and Yahoo are both practiced in the art of meeting short-term goals.

In the short and long term, analysts say, Google will have to add more services to combat Yahoo and Microsoft, Web portals and search service providers. It might, in fact, need to become more portal-like.

"Clearly, they're looking for ways to expand their reach," said Scott Kessler, an analyst for Standard & Poor's. "The fact that Google has a better mousetrap right now doesn't mean that they'll hold onto that No. 1 place."