Online lending company eloan.com recently offered to pay Yahoo! as much as $5.33 every time someone searching for the term "Pittsburgh mortgage" clicked on its Web link. That bid was enough to put the company at the top of the popular search engine's "sponsored" links for those words.

Four hours later, only the company's willingness to raise the ante to $6.02 a click -- even accidental ones -- kept it ahead of dozens of other bidders.

As consumers, researchers and school children become more and more addicted to Google and Yahoo! for checking out appliances, studying diseases and doing homework, businesses from Pittsburgh to Puerto Rico are spending more money -- and time -- to turn up on top in their search results.

Advertisers in the United States and Canada spent $5.75 billion on search marketing last year, a 44 percent increase over the year before, according to the Search Engine Marketing Professional Organization, in Wakefield, Mass.

More than 80 percent of that money went to paid placement, a term that refers to the sponsored links usually shown in a shaded box at the top or side or bottom of a search results page. Those are the only search results that are up for bid.

Each search engine has its own method for finding and ranking the non-biddable searches. Google, for example, uses an algorithm that rates a page's content as well as the number of other pages linked to that site, while Yahoo! counts more on editors to decide where the sites best belong.

Bidding wars for the "sponsored" words are playing out daily. Bidders can submit new offers 24 hours a day through accounts set up with the search engine operators.

Information on how to bid isn't hard to find. Under the familar Google.com search box, there's a helpful link to advertising programs or to information "about Google" that can get people started. At searchmarketing.yahoo.com/rc/srch/ users can find tutorials and check bid prices. There are many more search engines but those two are the largest.

Prices for search terms vary widely.

The term "Pittsburgh plumber" was worth as much as $3 per click to Roto Rooter two weeks ago while J&A Heating and South Park Heating of Bethel Park was ready to pay as much as $2 per click on Yahoo! A check last week found both had slipped one notch after daytradesconnect.com entered a bid of $3.01.

"Pittsburgh dentist" last week drew a high bid of just 38 cents per click from a Web site called DoYouKnowAGood.com, which offers referrals, while the second highest bid was a 36-cent offer linking to Bethel Park dentist Dr. John Sartorio's Web site.

Is a plumbing call worth more than a dental customer? What is it worth to a local florist to be at the top of the list in February vs. April?

There does seem to be general agreement on one thing: Bidding on search terms can be addictive, expensive and baffling.

"It's not quite as bad as a gambling addiction but it's like that," said Greg Jarboe, spokesman for the search engine organization.

Proving how seriously companies take the bidding wars, he wrote an article for Search Engine Watch recently that discussed tactics such as "bid jamming, bid surfing and bid shadowing."

There are all sorts of ways to work the system. A search term that lots of people are bidding on can be expensive but sometimes there's something similar that will bring customers without costing as much. The Web is full of tools, including some provided by the search engines themselves, to help bidders research bids and come up with alternative terms.

Some firms even treat the search word market as it were the stock market, charting the rise and fall of prices.

In 2004, San Francisco search engine marketing firm Fathom Online created a keyword price index that tracks categories such as consumer retail terms and automotive terms. The goal, a company spokesman said, was to give media buyers a reference point to help in their bidding.

Demand is exploding. While the early days may have seen companies buying a few hundred or even a thousand terms, a sophisticated search engine campaign now could involve 10,000 search terms in hopes of directing consumers to a company's services.

Blattner Brunner ad executive Rick Gardinier has both advised clients and runs his own small search campaign for the Downtown ad agency. When he set up a campaign to raise awareness of BBDigital.com last year, his monthly budget was about $500.

He wanted his terms to stay near the top of the sponsored lists, which required regular monitoring. "You want to make sure other people aren't outbidding you. It's almost like a day trading thing."

Some days he got enough clicks that his account was billed $30, other days there was little traffic. Even when he had lots of hits, he had to figure out if the clickers just wanted jobs or were prospects whose business would help justify the marketing expense.

It's not worth even 10 cents per click if people are looking for something else entirely, say information on spiders rather than Web design services.

Blattner Brunner, like many ad agencies, often advises clients to include search campaigns as part of their overall marketing. But tracking the shifting bids on thousands of terms, sifting through the clicks and determining who is clicking and why is more than a full-time task.

In such cases, the agency refers clients to firms, including Bridgeville-based Impaqt, that have software to follow the Web activity. Large search campaigns can start at $50,000 a year, by some estimates.

Yet, there's still room in this wild and woolly market for those with a lot less money, some time and a way with words. "The little guy can win. He just can't win accidentally," said Mr. Jarboe.

Small players may bid on variations of terms rather than go for the most popular ones. They can make a run at one key term in one market, slipping under the radar screen of a company blanketing the country.

Or, companies can try to slip into a searcher's field of vision the old-fashioned way, through what the industry calls an organic search. That means putting content on a Web page that somehow convinces automated search engine "bots" to rate a site as being useful and include it near the top of the non-sponsored links, which often number in the tens of thousands.

The search engines keep trying to come up with new ways to find the best sites and to weed out spam or those sites that try to hijack people by offering, say, porn instead of information on diabetes.

Perhaps because of all the hurdles, organic searches only claimed about 11 percent of marketing dollars last year, according to the search engine marketing association. "That's really difficult for someone who isn't very experienced to tackle successfully," said Mr. Jarboe.

Antique collector Tim Sweet had one of those satisfying moments in December when he decided to feature a type of ceramic known as yellowware on his whatsinyourattic.com site.

Mr. Sweet, who is senior sales consultant for Nauticom Internet Services in Sewickley, posted several paragraphs, trying not to use the term "yellowware" more than 4 percent of the time so it wouldn't be classified as spam but also to include enough content to lure the search bots.

Within three weeks, his listing showed up at the top of MSN.com's "yellowware" search -- at no cost.

And he has managed to sell some yellowware, too.