Our web app which is sold as a product to be installed on enterprise intranets suppoerts IE 7+. We dropped IE 6 recently and nobody complained thus far. Of course we also support Firefox, Safari, Opera and Chrome, but that's boring: my testing algorithm is as follows:
- develop in Firefox
- frequently test and fix on IE8 in compatibility mode
- frequently test and fix on IE8 regular mode
- sometimes test real IE 7 (so far IE8 in comp. mode has been 100% correct emulating IE7)
- before release confirm that Opera, Safari and Chrome are still correct. These 3 are almost always correct provided Firefox works.
