The syntax for compatibility mode is:
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE9" >
The content attribute specifies the mode for the page; to mimic the behavior of Internet Explorer 7, specify IE=EmulateIE7. Specify IE=5, IE=7, IE=8 or IE=9 to select one of those compatibility modes. You can also specify IE=edge to tell Internet Explorer to use the highest mode available.
Understanding Document Compatibility Modes
Internet Explorer supports a number of document compatibility modes that enable different features and can affect the way content is displayed:
- IE9 mode provides the highest support available for established and
emerging industry standards, including the HTML5 (Working Draft), W3C
Cascading Style Sheets Level 3 Specification (Working Draft),
Scalable Vector Graphics (SVG) 1.0 Specification, and others.
- IE8 mode supports many established standards, including the W3C
Cascading Style Sheets Level 2.1 Specification and the W3C Selectors
API; it also provides limited support for the W3C Cascading Style
Sheets Level 3 Specification (Working Draft) and other emerging
standards.
- IE7 mode renders content as if it were displayed in standards mode by
Internet Explorer 7, whether or not the page contains a
<!DOCTYPE>
directive.
- Emulate IE9 mode tells Internet Explorer to use the
<!DOCTYPE>
directive to determine how to render content. Standards mode
directives are displayed in IE9 mode and quirks mode directives are
displayed in IE5 mode. Unlike IE9 mode, Emulate IE9 mode respects the
<!DOCTYPE>
directive.
- Emulate IE8 mode tells Internet Explorer to use the
<!DOCTYPE>
directive to determine how to render content. Standards mode
directives are displayed in IE8 mode and quirks mode directives are
displayed in IE5 mode. Unlike IE8 mode, Emulate IE8 mode respects the
<!DOCTYPE>
directive.
- Emulate IE7 mode tells Internet Explorer to use the
<!DOCTYPE>
directive to determine how to render content. Standards mode
directives are displayed in Internet Explorer 7 standards mode and
quirks mode directives are displayed in IE5 mode. Unlike IE7 mode,
Emulate IE7 mode respects the <!DOCTYPE>
directive. For many web
sites, this is the preferred compatibility mode.
- IE5 mode renders content as if it were displayed in quirks mode by
Internet Explorer 7, which is very similar to the way content was
displayed in Microsoft Internet Explorer 5.
- Edge mode tells Internet Explorer to display content in the highest
mode available. With Internet Explorer 9, this is equivalent to IE9
mode. If a (hypothetical) future release of Internet Explorer
supported a higher compatibility mode, pages set to edge mode would
appear in the highest mode supported by that version. Those same
pages would still appear in IE9 mode when viewed with Internet
Explorer 9.
Because edge mode documents display webpages using the highest mode available to the version of Internet Explorer used to view them, it is recommended that you should only use this document mode for testing purposes only. Do not use it for production uses.
For more information on IE compatibility mode, check this out.