Opera Software co-founder and former CEO Jon S. von Tetzchner announced he is leaving the browser company in one week's time, giving no word as to what his next move will be.

Von Tetzchner had been serving in an advisory position after stepping down from his position as CEO last year, and his resignation today came as the result of differences he held from the executive board.

In an email message to Opera employees, von Tetzchner said "I feel the Board and Management is more quarterly focused than me. I have always worked to build the company for the future."

Indeed, current CEO Lars Boilesen's farewell message to von Tetzchner highlighted his drive to innovate the popular Opera web browser, and his priority to make the browser a "first mover." However, Boilesen made the goal to grow the company equally clear: "We are aiming at 500 million users by 2013."

As of May 2011, Opera and Opera Mini were ranked fifth and sixth in total browser market share claiming about 3.3% of the global market as users. As a desktop browser, Opera's growth has been relatively flat since 2009, but as a Mobile browser, the various versions of Opera lead the market, but have been trending downward over the last year as the use of Android's stock browser steadily gobbles up market share.

"It is of course a choice that brings up a lot of emotions", von Tetzchner said in an official announcement. "When we first started out, we were a few guys in a really small office - now we are spread all over the world, have over 740 employees and over 200 million users. I am very proud of what we have accomplished, and look forward to following the company closely also in the future."