It seems to be based on this dataset, which doesn't provide a breakdown of Firefox versions: http://www.w3schools.com/browsers/browsers_stats.asp http://www.w3

It seems to be based on this dataset, which doesn't provide a breakdown of Firefox versions: http://www.w3schools.com/browsers/browsers_stats.asp http://www.w3schools.com/browsers/browsers_stats.asp Note that this is from w3schools.com, not w3.org (a completely different site). This is for a web developer audience, so it kind of makes sense; from a developer point of view there are much bigger differences in standards compliance between IE versions than between Firefox versions. But mostly they just seem to want to keep a small number of columns on that page.