How many IE rendering modes are out there?

Question

I think we've all heard about different IE rendering modes, mostly based on their versions (IE6, IE7, IE8, IE9), their "compatibility mode", "quirks mode" and the emulation of previous version rendering. This is, that rendering IE9 simulating IE8 will not get the same rendering as native IE8.

Disregarding the big amount of Windows Versions these may run on... how many of those combinations are actually different? Should I consider IE9 running IE8 document mode when testing my websites? Should I just go with the major versions?

I'm honestly quite confused about the whole set of rendering engines for the Microsoft world alone, not yet to mention how Webkit, Gecko and other rendering engines may be behaving. I hope this question brings me (and others) closer to clearing our thoughts.

Answer 1

In the standards support profile for Internet Explorer, the term "document mode" is used to refer to modes in which later versions of IE emulate older versions (see [MS-IEDOCO] section 2.1.2, page 8).

• IE7 supports quirks mode and IE7 mode.
• IE8 supports quirks mode, IE7 mode, and IE8 mode.
• IE9 supports quirks mode, IE7 mode, IE8 mode, and IE9 mode.

Beyond the Document Mode settings, each browser engine can be used. So for instance, in IE9 you can render a page in IE8's engine, using IE9's document standard, so there are more combinations than you'd like to know about...

You can observe these rendering settings in the browser. In IE9, press F12 to see the developer's tools. There are two drop-down boxes at the top of the pane that allow you to set these values and re-render the page.

Note that "compatibility mode" is not a separate document mode. Note also that the standards mode of each version may implement the different standards differently from that version's document mode in a later version (for example IE7 standards mode versus IE7 mode in IE8). See the other documents in the standards support profile for more information.

Moreover, an additional document mode is supported in IE8, and IE9, namely "almost standards mode": If the page contains an XHTML or HTML Transitional or Frameset DOCTYPE declaration (p. 15), "the layout of images inside table cells" will be "handled the same way that quirks mode handles it." (p. 9)

Answer 2

If you are looking for testing what X-UA-* types acts in different IE versions look here: http://emological.com/ie/