One week after Yahoo named co-founder Jerry Yang as CEO, the company promoted David Karnstedt to head of North American sales, continuing a company restructuring that began in December 2006.

Yahoo also announced plans to merge its search and display advertising units. In December, the company reorganized into three divisions: the Audience Group, the Advertiser & Publisher Group, and the Technology Group, the heads of which all report to the CEO.

With Karnstedt's appointment as head of North American sales, U.S. chief sales officer Wenda Millard will leave the company immediately, Yahoo said.

Keeping up with Yahoo's executive arrivals and departures since the December shake-up requires a scorecard.

Upon announcement of the three new corporate divisions in December, the company announced Chief Operations Officer Dan Rosenzweig would move on, departing in March.

Also in December, former Chief Financial Officer Susan Decker became head of the Advertiser & Publisher Group, before being named president of Yahoo last week. Decker will continue to oversee that group, and will also have the Audience Group in her portfolio. The Technology Group was headed by Chief Technology Officer Farzad Nazem until he left the company June 8.

Yahoo's other co-founder, David Filo, will lead the Technology Group until Nazem's replacement is named.

Former CEO Terry Semel stepped down last week to make way for Yang, but will remain with Yahoo as non-executive chairman.