Testing for every browser is a costly and time consuming excercise and I have put a lot of thought into how we get the best result for our clients and their customers while keeping the cost under a million dollars . Heres what we do ....
We manage future bowser version compatability by developing using the W3C guidelines for world wide web standards
We manage browser compatibility by testing to the following browsers:
* Internet Explorer(IE) 6, 7 & 8
* Firefox 2 & 3
* Safari - Mac & iPhone
Roughly 60% of the market (Net Applications via Wikipedia) is using IE. IE6 & IE7 do not fully support the world wide web standards so we sometimes go away from the standards in order to make things work in IE, which is the major web browser. Of course we check everything works fine in the other browsers at the time, but new browsers and new versions of the browsers can be, and will be, realeased after we have delivered the project.
When new browser versions are released we check that our Nautilus software works in the new release but not custom built software.