Yahoo's revolving door of CEOs (pictures)

Yahoo as we know it will soon be gone. The long-struggling Internet pioneer said Wednesday that it plans to spin off its core business, which would ultimately make it easier to sell off that business.

The CEO since 2012, Marissa Mayer had tried to turn the company around and lure consumers back to products like Yahoo Mail and the thing that got it all started, search. It wasn't enough.

Yahoo's woes started before Mayer took the reins. Here's a look back at the Internet pioneer's leadership over the years.

CNET's Rich Nieva contributed to this gallery.

Tim Koogle, Yahoo's first chief executive, led the company from 1995 till May of 2001. A veteran of Motorola, he was viewed as a steady, seasoned professional and the perfect complement to Yahoo founders Jerry Yang and David Filo, who created the site in 1994 while attending graduate school at Stanford.

Koogle built Yahoo into a Web powerhouse and guided the company through its initial public offering in 1996. But he was no match for the dot-com bust. The company's stock took a dive in 2000 as other Internet companies, which Yahoo relied on for advertising, slashed their marketing budgets.

Koogle stepped aside as CEO in 2001 as Yahoo looked to transform from just a dot-com into a more traditional media company.

Terry Semel was CEO of Yahoo from April 2001 to June 2007. The veteran Warner Bros. executive was viewed as a risky choice to lead an Internet company, but the move appeared to work at first. Semel was given credit for wrangling the company's sprawling divisions and expanding its business through an array of acquisitions and partnerships.

But Yahoo missed out on some big deals -- including buying both Google and Facebook -- and was unable to keep pace with younger Web rivals. In particular, Yahoo was slow to build a successful search ad business and got left behind by Google.

In 2007, co-founder Jerry Yang replaced Semel as CEO and set out to take a piece of Google's commanding share of the search market.

Yahoo co-founder Jerry Yang took on the role of chief executive from June 2007 to January 2009. Most notably during his bumpy 18-month tenure, Yang rejected Microsoft's $44.6 billion bid to acquire Yahoo. The company also struggled financially and cut more than 2,000 jobs.

Yahoo's stock continued to fall, and investors demanded new leadership. Carol Bartz, Autodesk's former executive chairman, replaced Yang as Yahoo's CEO in January 2009.

Carol Bartz was CEO of Yahoo from January 2009 to September 2011. The former executive chairman of Autodesk attempted to reorganize Yahoo to be faster and simpler, but the company continued to struggle. The Internet pioneer was unable to keep up with new rivals or regain ground lost to Google.

When Bartz's role at Yahoo came to an end, she said in an email sent to employees that the board had given her the sack. "I am very sad to tell you that I've just been fired over the phone by Yahoo's chairman of the board," Bartz wrote. "It has been my pleasure to work with all of you and I wish you only the best going forward."

Yahoo Chief Financial Officer Tim Morse was named interim CEO.

Tim Morse served as interim CEO from September 2011 to January 2012. In charge of the company for only a few months, Morse mostly batted away questions about Yahoo's future as rumors swirled that it was considering takeover offers.

Morse returned to his role as chief financial officer when former PayPal President Scott Thompson took over as Yahoo CEO.

Scott Thompson was CEO of Yahoo from January 2012 to May of the same year. During his short time at the company, the former PayPal president launched a patent battle against Facebook and orchestrated layoffs.

Thompson left Yahoo after he was accused of having inflated his college credentials, and Yahoo's global media leader, Ross Levinsohn, was named interim CEO.

Ross Levinsohn took the job of interim CEO from May to July of 2012. Levinsohn, who led Yahoo's global-media business, did his best to stabilize the company after the departure of Scott Thompson. Levinsohn was considered a front-runner for the permanent job until Yahoo's board named Marissa Mayer, a key Google executive, as the next CEO.

Marissa Mayer, a former Google executive, took the helm at Yahoo in July 2012. She tried to remake the Internet pioneer for the mobile era as consumers migrated to smartphones and tablets from PCs. Mayer refreshed each one of the company's mobile properties, including Yahoo Mail, Weather, Finance and Sports.

She also tried to make Yahoo a premier media destination by hiring personalities like journalist Katie Couric and acquiring the rights to shows like the sitcom "Community."

But Yahoo still struggled to create excitement around its products. Once one of the most powerful sites on the Internet, Yahoo had been overtaken in search and email by Google and beaten in media by Netflix and Amazon. Meanwhile, Facebook and younger players like Snapchat gobbled up users that Yahoo coveted for its messaging apps.