Considerations for site audits and testing on IE9?

Question

Now that Internet Explorer 9 has a growing market share (5.63% at time of writing, and closing in on IE7 fast), what are some of the major considerations for people wishing to test sites and web applications developed for IE8 (and under) support?

The main point of call so far is Microsoft's IE9 feature list. One of the most standout issues is checking that MIME-types are defined correctly, but I'm interested to hear what other testers have encountered as useful or noteworthy.

Answer 1

Concentrate on Design/ UI issues mainly, Check for CSS style issues, Check how the session and cookies are handled in IE9 to test remember me function or auto singout, I got one problem with this in IE9. IE9 compatibility with various scripts like java script, Ajax or JQuery.