What a ride it has been for a former Google star who is trying to right the ship at a fallen 90s tech star. Marissa Mayer at Yahoo? Sure, but also Tim Armstrong. He shares Ms Mayer’s Google heritage and sits at the helm of AOL – an experience that may be a useful benchmark for Ms Mayer and Yahoo shareholders.

Yahoo shares are up 70 per cent in the year since Ms Mayer was named chief executive but yesterday’s second-quarter results show the operational turnround is still a work in progress. Display ad revenue fell 11 per cent, the second straight quarter of a double-digit decline. Overall revenue was flat and earnings missed expectations. Importantly, investors also learnt that Yahoo is valuing its Asian investments, Yahoo Japan and the Chinese internet retailer Alibaba, collectively at $18bn. That looks modest since Alibaba’s valuation is based on a funding round from last autumn but it still means that over 60 per cent of Yahoo’s market capitalisation is coming from non-core investments.

Ms Mayer must eventually translate pricey acquisitions, such as Tumblr, and product redesigns into top-line growth. And while many still write off Yahoo’s core internet business, Mr Armstrong’s experience at AOL is instructive. He has been CEO since early 2009, the year that AOL was spun out of Time Warner and began trading. Shares had lost half their value by mid-2011 as investments were slow to bear fruit but have rebounded to 60 per cent above the original listing price. In its most recent quarter, AOL was able to show ad revenue growth across all its platforms for the first time in five years. Mr Armstrong has invested heavily in building content and platforms that advertisers want, as has Ms Mayer.