Last Friday, 16 January, Adam published the revised browser testing guidelines, and he’s done a great job of including best-practice development. The guidelines point to the BBC’s support table as a good example of graded browser support, and notes the importance of supporting standards-compliant browsers (paragraphs 17-18):

Coding a site to web standards should ensure that any browser that supports web standards will render and behave as intended. Therefore your browser testing matrix must include browsers that support web standards.

You should follow a progressive enhancement approach to developing websites to ensure that content is accessible to the widest possible number of browsers.

The importance of valid code is noted (paragraphs 21-23):

All (X)HTML content must validate with respect to your chosen DTD.

You must use valid CSS for the presentational layer of your website including layout and styling. (X)HTML tables should only be used for presenting tables of data.

Code used for adding richness to the user interface (e.g. JavaScript, ActionScript) must be ECMAScript-compliant.

The guidelines now emphasise functionality over identical layout across browsers (paragraph 39):

You should check that the content, functionality and display all work as intended. There may be minor differences in the way that the website is displayed. The intent is not that it should be pixel perfect across browsers, but that a user of a particular browser does not notice anything appears wrong.

Graceful degradation without scripting/ plug-ins and accessibility are required (paragraphs 41-42)

You should also test your website to make sure that it works with scripting and plug-ins turned off.

Some users will be unable to use pointing devices so you should verify that the site works using a keyboard only.

It’s a job well done.