This. Your documents should use progressive enhancements that make them at least accessible (if not pretty) with every browser that has ever existed. If you wri

This. Your documents should use progressive enhancements that make them at least accessible (if not pretty) with every browser that has ever existed. If you write something that only works on FF5 or IE9, you did something wrong, and someday we'll be cursing you just as you curse people who wrote stuff that only work on IE6.