NEW YORK — Microsoft owned up to the collapse of its biggest push into digital advertising, saying Monday that it will take a $6.2 billion accounting charge — essentially a write-off of the value of aQuantive, a digital ad firm Microsoft bought in 2007.

The company said ‘‘expectations for future growth and profitability are lower than previous estimates’’ for the online services unit. The charge will not affect the online services division’s operations or financial performance, Microsoft said.

The deal for aQuantive was struck when technology and traditional advertising firms were desperately seeking footholds in the world of Internet display advertising. A month before the aQuantive acquisition, Google, Microsoft’s big rival in online advertising, purchased a similar firm, DoubleClick, for $3.1 billion. That deal has been highly profitable for Google, analysts say.

Microsoft bought aQuantive one day after WPP Group bought 24/7 Real Media, another digital advertising company, and a month after Yahoo agreed to buy Right Media, an online ad exchange.

All of the acquisitions were in one or another part of the display advertising business across the Web. Once highly profitable, the business came under pressure as companies like Google got better at aiming for individual tastes with search advertising.

.