Former CBS anchor Dan Rather had been under attack from conservatives before, but online bloggers dealt the fatal blow to his anchoring career last fall when their questions about documents in a CBS report on President Bush's National Guard service forced the admission that the information had not been authenticated.

It was a pivotal point not just for Rather -- the longtime face of the CBS Evening News ended up resigning in March and taking a reassignment -- but for many public relations executives, too.

The industry has watched the online world explode with the emergence of so-called bloggers, people who self-publish on the Web, often writing daily journals or Web logs -- blogs, for short -- about their observations. But with the impact growing as fast as the number of blogs out there, PR firms realized it was time to act before their clients found themselves caught in a virtual storm.

In the past three months, large traditional firms Ketchum and Burson-Marsteller and small Web development and online marketing agency Ripple Effects Interactive, all with offices in Pittsburgh, have unveiled services to help clients manage and shape their online reputations.

The goal is to sell clients on using PR experts to sort through the confusing world of blogs, search engine marketing and other technologies such as podcasting before the online world turns on them.

"We saw it [coming] in the spring and said, 'we need to jump on this,' " said David Heidenreich, director of strategy and online planning for Ripple Effects, which launched its online relations practice last month.

The challenge to public relations management presented by online conversations is daunting.

Estimates last spring put the number of online diaries at around 9 million; blog tracker Technorati now says there are more than 15 million. And Nielsen/NetRatings calculates that the top 50 blogging and blog-related sites grew 31 percent between the beginning of the year to July, pulling 29.3 million visitors -- nearly one in every five active Internet users.

Though long involved in designing Web advertising and helping clients attract online attention, Ripple Effects discovered firsthand the power of the blog through a marketing project done this summer for the Pennsylvania tourism department.

The company hired people to wander around the state and write about their experiences in an online journal that anyone could read. The project, which used about 20 people, generated more than 200 mentions in traditional media and online sites, Heidenreich said.

Corporate clients vary in their awareness of the blog world.

Some already use technology to track references, whether they show up in harmless chats about the weather or potentially damaging discussions of bad service. But, the agencies say, many companies are barely aware of all the content that Internet users are posting and of the more simple fact that, in the online world, the past never dies.

A recent checkup done for a Burson-Marsteller client, for example, found a query that a job hunter had posted in 2001 asking about what it would be like working for the client in question, a Lehigh Valley Fortune 500 concern. Just a few weeks ago, someone answered with a scathing response: "I just left. Run for the hills."

Because the online world is so fast, some agencies may partner with such Web tracking companies as Intelliseek, which monitors online "buzz" and has worked with both Ketchum and Burson-Marsteller. But public relations agencies still rely on their expertise in choosing whether and how to respond to what's uncovered.

Sometimes, research will show a Web site or blogger has few readers, which means responding would just escalate the problem. But a commentary that picks up momentum among others plugged into the Internet may also highlight a business problem that a company needs to address.

One of the biggest public relations challenges may be the bloggers themselves.

Agencies and their corporate clients must tread carefully. The beauty of the online journals has been their very casual format, sometimes brutal opinions and under-the-radar sensibility.

Ketchum's announcement in June that it would be launching a service advising organizations on how, why and when to use blogs, podcasting -- publishing audio and video broadcasts on the Internet -- and other online tools drew a raft of criticism from a number of bloggers.

They questioned how a company that does not have its own blog and does not offer an RSS feed on its Web site (Really Simple Syndication, or RSS, lets bloggers share headlines and content from other sources) could help anybody else.

"Better advice for the blog-lorn is much more likely to come from people who really understand the social dynamics in the blogosphere," wrote Stowe Boyd, who is described in his online bio as president and chief operating officer of Corante and "a well-known media subversive."

Adam Brown, the Pittsburgh-based director of eKetchum who will be heading the blog and search engine pieces of the new personalized media product, is well aware of the criticism.

"We actually took a bit of our own advice (the same advice we share with our clients) and wanted to measure and monitor the blogosphere before going out with our own blog," which it is doing this month, he said in response to an e-mail question.

Ketchum helped create a blog for Food Network chef Tyler Florence (www.tylerflorenceblog.com), who is known for wandering around the world. The chef's letters on the blog, which include recipes, read sort of like an online cooking show as opposed to travels with a foodie.

Getting the tone right is not easy. In many cases, the agencies agreed, a corporation trying to blog comes off as badly as a parent trying to be cool.

The often stilted, corporate-speak of a chief executive officer may be seen as more of the same rather than as a company using a new outlet to add a human touch and allow readers to be part of a real conversation.

"You don't want to come across as if your message is contrived or manipulative or misplaced," said Ripple Interactive's Heidenreich. The worst kind of blogs, he added, are those that just push out marketing fluff.

He thinks public relations professionals can play a role in interpreting this brave new world -- even if they are not die-hard bloggers. But he sympathizes with those who don't think its a compliment that the corporate world is starting to pay attention.

"It's like when your favorite band becomes popular," Heidenreich said.