Our research shows IE 6 at 4% of the market and our numbers take the most optimistic results. I have seen other at 3% with a more pessimistic model. We recomme

Our research shows IE 6 at 4% of the market and our numbers take the most optimistic results. I have seen other at 3% with a more pessimistic model. We recommend to out clients that they use the compounding development cost of chasing IE 5-6 and non-JS browsers and apply it to targeting mobile platforms. You get more bang for your buck doing so. By eliminating IE < 7 and none JS browsers you are walling yourself of from a little less than 10% of the market but the development effort to chase them increased development cost nearly 2x, targeting the iPhone (especially if your web was built with a REST backbone) is significantly cheaper 5K is the average app build, will net a better return on investment. As well some assumptions can be made about older browser uses, they are either not early adopters or are using a corporate PC and may have access to a more modern environment at home or via a mobile device while not quantifiable, these factors will certainly work to reduce that total market size of non-modern browsers. As I always say to clients, if you get to the point where you have to chase that < 10% for growth you have a good problem.