HTML and CSS Reference
For the purposes of development, testing, and ongoing support, it may
be useful to explicitly state which browsers or configurations will not
be supported. Visitors with older browsers such as Netscape 6, Internet
Explorer 5, or older mobile devices are F-grade browsers that will just get
what they get and have to make due.
X-grade browsers are assumed to fall into the A-grade category but
because of a small share of your user base or similarities to browsers
already listed as A-grade, they aren't on your radar or testing matrix.
Older point releases, Linux versions, or alternate UI browsers such
as Camino or Flock that use the same rendering engines as A-grade
browsers fit in this category.
It is increasingly useful to have an extra category called A+ -grade brows-
ers defined to allow for some extra flair above and beyond the A-grade
category. New CSS3 features such as rounded corners, animations, or
transitions can be used to enhance the experience for some visitors while
not being central to the site's design.
When you want to use the latest and greatest coding techniques on your
web site and when your business needs or your user base dictates that
you need an A- or B-grade level of support for a browser that otherwise
bridge support or implement alternative methods of achieving a similar