Mmm - more research solved this one - you can ignore this question.
As of November 2010 Apache served over 59.36% of all websites and over 66.56% of the million busiest.[
Web server growth in 2010
And now how web server usage changed in 2010:
•Apache went from hosting 109 million websites in 2009, to almost 152 million by the end of 2010.
•Net result: Almost 43 million new Apache websites in 2010.
•Microsoft IIS went from hosting 49 million websites in 2009, to almost 57 million by the end of 2010.