IE8 Browser Mode and Document Mode

Browser Mode: IE7 / IE8 / IE8 compability view
Document Mode: Quirks Mode / Ie7 standard / Ie8 standard
Discovering Internet Explorer Developer Tools

Testing Browser Modes
The Browser Mode menu lets you choose how Internet Explorer should report three important properties:
* User agent string: The value Internet Explorer sends to Web servers to identify itself.
* Version vector: The value used when evaluating conditional comments.
* Document mode: The value used to determine whether Internet Explorer uses the most recent behavior for CSS, DOM, and JScript operations or emulates a previous version of Internet Explorer for compatibility.

Three Browser Mode options exist, each modifying these values in different ways:
* Internet Explorer 7: In this mode, Internet Explorer reports a user agent, version vector, and document mode identical to those used by Internet Explorer 7. Use this mode to test how Internet Explorer 7 users experience your site.
* Internet Explorer 8: In this mode, Internet Explorer reports a user agent, version vector, and document mode to match the default Internet Explorer 8 behavior, which is the most standards-compliant available in Internet Explorer 8. Use this mode if you want to test how Internet Explorer 8 users experience your site.
* IE8 Compatibility View: In this mode, Internet Explorer 8 reports version vector, document mode, and user agent string as if it is Internet Explorer 7; however, the user agent string also includes a token indicating that the browser is really Internet Explorer 8. Use this mode to test how Internet Explorer 8 users experience your site if they've chosen the Compatibility View option.

Testing Document Modes

The Document Mode defines how Internet Explorer renders your page, but has no effect on the version vector or user agent string. By using this option in conjunction with the Browser Mode, you can quickly test which document mode you should use for your site. Three options exist:

* Quirks Mode: This behavior matches that of Internet Explorer when rendering a document with no doctype or a Quirks doctype. It's similar to the behavior of Microsoft Internet Explorer 5 and the Quirks mode behavior of Internet Explorer 6, and the same as the Quirks mode of Internet Explorer 7.
* Internet Explorer 7 Standards Mode: This behavior matches that of Internet Explorer 7 rendering a document with a strict or unknown doctype.
* Internet Explorer 8 Standards Mode: This behavior is the latest standards-compliant available in Internet Ex