We’ve decided that IE8 will, by default, interpret web content in the most standards compliant way it can. This decision is a change from what we’ve posted previously.
Microsoft recently published a set of Interoperability Principles. Thinking about IE8’s behavior with these principles in mind, interpreting web content in the most standards compliant way possible is a better thing to do.
We think that acting in accordance with principles is important, and IE8’s default is a demonstration of the interoperability principles in action. While we do not believe any current legal requirements would dictate which rendering mode a browser must use, this step clearly removes this question as a potential legal and regulatory issue. As stated above, we think it’s the better choice.
The rest of this blog post provides context around the different modes, the technical challenge, and what it means going forward.
Clear terminology around the different modes in IE8 (as well as other browsers) is crucial for the discussion. Wikipedia, as usual, offers a good starting point. The article about “Quirks mode” describes how modern browsers (like IE, Firefox, Safari, and Opera) all have different modes for interpreting the content of a web page: Quirks and Standards. (The article also covers “Almost Standards;” let’s set that one aside for the purpose of this discussion.)
Basically, all the browsers have a “Quirks” mode, call it “Quirks mode", and use it to offer compatibility with pages that pre-date modern standards. All browsers have a “Standards” mode, call it “Standards mode,” and use it to offer a browser’s best implementation of web standards. Each version of each browser has its own Standards mode, because each version of each browser improves on its web standards support. There’s Safari 3’s Standards mode, Firefox 2’s Standards mode, IE6’s Standards mode, and IE7’s Standards mode, and they’re all different. We want to make IE8’s Standards mode much, much better than IE7’s Standards mode.
Read More @ the Microsoft IE Blog