Google (Nasdaq: GOOG), operator of the world’s most popular search engine, is upgrading its online advertising service to make it easier for marketers to reach users on different devices.

And Yahoo (Nasdaq: YHOO) is hoping to cash in on Google’s expertise.

The revamped Google AdWords service will also help companies manage bids for ads running at different locations and times, according to a blog post Wednesday. Using an auction system, Google sells advertising keywords that are displayed alongside search results.

While there may be new tools for marketers, some of the changes also mean Google’s average ad price will rise, according to Bill Mungovan, a director of product marketing and strategy for media and advertising solutions at Adobe Systems Inc. Mungovan said advertisers will no longer be able to separately purchase tablet spots, which cost less than those for desktops — a change that will boost average prices.

“This, presumably, will address Google’s mobile monetization gap as an increasing share of searches is coming from tablets and smartphones,” Mungovan wrote today in a blog post.

Last month, Google said the average price of its ads dropped 6 percent in the fourth quarter from a year earlier.

Google is aiming to boost mobile advertising as users increasingly rely on smartphones and tablets for their computing and communication needs. Google’s mobile revenue from search-based advertising more than tripled in the fourth quarter from a year earlier, according to analysts at Stifel Nicolaus & Co. Over the past year, Facebook (Nasdaq: FB) has built up mobile advertising, which makes up 23 percent of its total ad revenue.

“This is a first step to help you more simply and smartly manage your ad campaigns in today’s multidevice world,” Sridhar Ramaswamy, senior vice president of engineering, wrote in the blog post.

The overhaul will also let companies track the performance of their advertising campaigns, with tools that measure what happens after users see ads.

Google Makes Acquisition

Google also says it has agreed to buy Channel Intelligence Inc. for $125 million, adding online marketing tools that retailers use to bolster Internet sales.

The transaction is expected to close in the first quarter, according to a statement from Radnor, Pennsylvania-based ICG Group Inc., which jointly owns Channel Intelligence with Aweida Capital Management. Channel Intelligence helps retailers refine online sales pitches and promote goods on Facebook Inc.’s social network.

Google is stepping up efforts in e-commerce after announcing plans last year to transition its product- search feature to a paid commercial model in the U.S., requiring retailers to purchase space on the new Google Shopping service.

In November, Google acquired BufferBox Inc., a service for delivering e-commerce goods to physical kiosks.

“Our vision for CI started with the desire to simplify the online shopping experience,” Rob Wight, founder and chief executive of Channel Intelligence, said in the statement.

Yahoo’s Move

Yahoo, meanwhile, is counting on rival Google to help accelerate its revenue growth.

As part of a nonexclusive arrangement announced Wednesday, Yahoo’s website will begin drawing upon Google’s massive online advertising network to show marketing messages related to the content that’s being perused.

Google already distributes similar ads to thousands of websites, a service that has helped establish it as the Internet’s most prosperous company.

Yahoo has been struggling to attract more advertisers in recent years, even though more marketing budgets have been shifting to the Internet. The company’s revenue had fallen in three consecutive years before registering a small gain last year. Yahoo CEO Marissa Mayer, a longtime Google executive before being lured away nearly seven months ago, has pledged to produce more impressive growth in future years.

Google retains part of the revenue generated from the ads shown on its partners’ sites. The revenue split with Yahoo wasn’t specifically disclosed, but Google has previously said that website owners that display the kind of ads covered in this agreement usually get to keep 68 percent of the revenue.

Last year, Google’s ad sales on its partners’ sites totaled $12.5 billion. That amount includes ads shown next to the search results on other websites, a service it isn’t providing to Yahoo.

That’s because Yahoo already depends on Microsoft for most of its search-driven advertising as part of a long-term deal signed in 2009. Yahoo aligned itself with Microsoft Corp. after a proposed partnership with Google in 2008 unraveled when the U.S. Justice Department threatened to file a lawsuit to block it. The Justice Department contended that Google would have been able to use its dominance of Internet search to thwart competition if it were able to expand its reach on to Yahoo’s popular website.

This time around, Google and Yahoo aren’t working together in search advertising.

Analysts have been predicting that Mayer’s old ties with Google might eventually lead to a closer relationship with Yahoo.

Yahoo’s chief operating officer, Henrique De Castro, is also a former Google executive.