Search engine marketers praised the move, saying it gives advertisers far more control over where their ads will appear. "Google is really responding to their customer base here. From what I understand, this is a direct result of information they're getting from their customers," said Gregg Stewart, search engine marketing firm Fathom Online's senior vice president for channel management and marketing.

In the past, Stewart said, some search engine marketers were able to finesse the Google bidding market to get ads to show up in the content market, and not in the search results pages--but the process was inconvenient--and didn't always work. Now, with separate bid markets available for the content network--which encompasses every site that includes an AdSense ad unit--and the sponsored links in searches, the process is vastly simplified.

Bryan Wiener, CEO of SEM firm 360i, said that the change also will allow advertisers to determine the return on investment for search ads and contextual ads separately. Before, a click from a sponsored link from a search was indistinguishable from one from a content page.

"Anything that's going to allow marketers to look at the ROI of various components is great news," Wiener said.

Google competitor Yahoo! has allowed advertisers to bid separately for sponsored links on their Yahoo! Publisher Network since its inception.

Jupiter Research Analyst Gary Stein wrote on his blog that Yahoo! got some early goodwill by offering the more flexible alternative. "Whether these two programs should be run as separate marketplaces has been a question hanging over Google's head since they introduced the program," he wrote. "In fact, Yahoo!/Overture got a lot of mileage out of separating the two in their offerings."

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