Google has bought online ad firm Admeld in order to get the most out of the rapidly evolving display ad industry the company confirmed today.

While Google would not comment on its price, various media sources indicate the deal was for $400 million. The price makes Admeld Google's sixth most valuable acquisition from a dollar standpoint.

Admeld, which is three years old, is a yield optimization provider. The company works with publishers and helps them maximize revenue through data analytics and other services. Admeld acts a middle ground between publishers and marketers, working with publishers to lock up contracts, integrations and billing.

In a blog post announcing the deal, Neal Mohan, Google's Vice President of Display Advertising, said he hopes the deal ushers in an era of flexible ad management tools for major publishers.

Together with Admeld, we hope to make display advertising simpler, more efficient and more valuable, provide improved support and services, and enable publishers to make more informed decisions across all their ad space, Mohan said.

Mohan said he believes the display ad industry is potentially worth more than $100 in revenue for Google over the next few years. Last year, the company reached $30 billion in ad-based search revenue.

The company's last  biggest advertisement acquisition, DoubleClick, helped grow their display ad revenue by a factor of five.  DoubleClick, which Google bought for $3.2 billion, allowed the tech giant to create the DoubleClick ad exchange, which provides  a marketplace matching up buyers and sellers of ads.

What's driving this relationship is a shared belief that managing display advertising is still far too complicated for publishers, and together Admeld and Google can help address some of the underlying inefficiencies. Though we have no specific integration plans yet, we imagine our combined offerings can help publishers make more informed, efficient, and profitable decisions across all tiers of their inventory, Admeld chief executive Michael Barrett said in a blog post.

The deal will have to pass all the regulatory bodies before becoming official.

Follow Gabriel Perna on Twitter at @GabrielSPerna