While growth is slowing at most top Internet sites, it is skyrocketing at sites focused on social networking, blogging and local information.

The dramatic success of those Internet categories is apparent from a recent online-traffic analysis provided by market research firm ComScore Media Metrix, which examined visitor growth rates among the 50 top Web sites over the past year.

Top-ranked sites growing the most, ComScore's data showed, were Blogger.com, a personal publishing site; MySpace.com, where young people do virtual preening and share musical tastes; Wikipedia, an open reference site jointly edited by millions of people; and Citysearch, a network of local guides focused on cities.

The number of monthly visitors to each site rose at rates ranging from 185 percent (Citysearch) to 528 percent (Blogger.com) from February 2005 to February 2006. Their growth far exceeded the 4 percent increase in overall Internet visitors in the United States during that period.

The traffic analysis shows the Internet is still a space where new brands such as MySpace can suddenly break into the upper ranks, where older brands such as Citysearch can revive themselves after languishing for years, and where established outfits such as Google often wind up as beneficiaries because they buy or copy services pioneered by upstarts.

Google Inc., for instance, bought Blogger.com in 2003; the number of people posting or reading material at that site jumped to 15.6 million last month from 2.5 million a year ago.

"The growth in blogging reminds us the Internet is fulfilling its original promise about participation," said Gary Arlen, a research analyst and president of Arlen Communications Inc. "This medium empowers users in such a way that they can do what they want and be heard."

Peter Daboll, president and chief executive of ComScore Media Metrix, said one notable recent traffic trend is increased popularity of sites helping people find local information.

In addition to Citysearch, a network devoted to local entertainment and commerce, Daboll said, two local directories made the Web's top 50 last month, WhitePages.com and Verizon's Superpages.com.

Greg Sterling, an independent analyst, said local Internet services lagged behind their national counterparts for years but are finally coming on strong because they are much better today and people are more aware of their utility. "

ComScore usually lumps together sites owned by the same firm in its Internet traffic reports. So The Washington Post asked ComScore to break out traffic for the Web's top 50 individual sites to get an idea of which were gaining and losing momentum.

The analysis showed that the Internet's biggest brands have plenty of staying power or at least are keeping pace with growth in the overall online population. Yahoo retains the largest audience in the United States, though its visitor growth slowed to about 5 percent last year.

Google was the only mega-site bucking the trend, with its users shooting up 21 percent in the past year.

For a chart showing all top 50 Web sites and their number of visitors last month, go online to washingtonpost.com/technolo gy.