To find out how much of my time I want to put into making the site I work on compatible with earlier browsers, I started a short search fro data on market shares. Statistics are tools you need to be truly careful to use, and this search turned up results that clearly show this.
B-dk for instance says that Internet Explorer is the most used browser with a market share of 50% in this article. w3schools says that Internet explorer’s market share is only 16,2%, while GearNYT mentions a share of 23,7%.
That is a great span and just shows, that statistics tell you what you want to hear. I believe the factors in deciding which browser is the most used to so many and so complex, that there is very little meaning in those numbers, when it comes to deciding your own policy on the development for older browsers.
If your site keeps statistics on the browsers used to accesr it, than those are the numbers you want.
My own site (this one) says that my site is viewed in Firefox by 47.4% of the visitors and that Internet Explorer makes it as number three with 19.2% . IE9 takes 6.7% of those and IE8 7.1% while the “culprit” IE6 still has as much as 4,9% even though Microsoft has declared this ancient browser for dead.
But the site I currently work on says, that among it’s users as much as 54.27% use IE9, 29.7% use IE8 and 0,3% use IE6.
Again quite different numbers, but much more safe to work from than the numbers given by the others above, since these are the actual visitors to your site.
With the warning from Microsoft about the use of IE10 these numbers may change soon, unless they manage to make up for the problems before it is too late. (See these two danish articles:
Politiken and version2.dk