Netcraft uses several methodologies to measure the different market segments. For "active Sites" a methodology, which is dominated by webservers with low and medium traffic, Microsoft has dropped below 15% years ago; for "total sites" which is dominated by big webhosting companies and for "top million" which measures the big-traffic websites, Microsoft fell below 15% in recent months. |
The company Security Space does not just measure total market share, but also regional differences: The share in Japan, Germany, Russia and many other countries already lies below 4% for many years. But also traditionally Microsoft-friendly countries can turn away from IIS, for example in the last 10 years, the share in France fell from 35% to 5%, in Brazil and Taiwan from over 45% to 15% and in India even from 65% to 18%.
In more and more countries, Microsoft will face the problem that third parties (webhosters, IT-departments within companies, fleelancing programmers, etc.) don't even offer support for their products and the know-how is lost because Microsoft-webservers are seen more and more as a legacy-technology. Another problem for Microsoft is that existing customers have to upgrade to newer versions in order not to lose official support. For example more than two thirds of Microsoft-webserver still run with IIS 6.0, therefore on Windows XP or Windows Server 2003, both already beyond "mainstream support". In 2014/2015 the extended support will also be terminated. Even when Microsoft is probably able to make the majority of their customers to buy the same product again, they will lose a part of their users with every upgrade-cycle.
There is also a technical reason why Microsoft will lose market share in the future. So far, Microsoft's main competitor was the architecturally similar (synchroneous) Apache webserver. But since a couple of years there is (asynchroneous) nginx, which does not offer all the features of Apache or IIS, but is faster. Especially big websites like Facebook, Wordpress or Hulu are using nginx. When a website pushes it's limits, it may be cheaper to migrate from IIS or Apache to nginx, instead of buying new hardware and/or switch from one server to a cluster.
Probably Microsoft will lose their second place to nginx in 2012 or 2013 and will become a "legacy" system over the years.