1. Marissa Mayer will be Yahoo Inc.'s fifth CEO in five years, not including two interim CEOs. She's also the fourth interim or permanent CEO this year. Here's a look at the people who have had that top job over the years.
2. Tim Koogle - 1995-May 2001. Began tenure shortly after Yahoo was incorporated in March 1995. Announced in March 2001 that he would step down after a replacement is found.
3. Terry Semel - May 2001-June 2007. Hired from Warner Bros. Stepped down under shareholder pressure.
4. Jerry Yang - June 2007-January 2009. Company co-founder and de facto CEO until Koogle started. Agrees to resign under pressure in November 2008, pending appointment of replacement.
5. Carol Bartz - January 2009-September 2011. Hired from Autodesk Inc., a design and engineering software company. Fired after failing to revive the company.
6. Tim Morse - September 2011-January 2012. Interim CEO. Retained chief financial officer role during CEO stint.
7. Scott Thompson - January 2012-May 2012. Hired from eBay Inc.'s PayPal. Left after disclosure that his official biography included a college degree he never received.
8. Ross Levinsohn - May 2012-July 2012. Interim CEO. Joined Yahoo in November 2010 following a stint running Internet services at News Corp.
9. Marissa Mayer - Starts as CEO on Tuesday, 17 July 2012. Most recently in charge of mapping, location and local services at Google.