Compatibility Modes
Document compatibility modes determine how Windows Internet Explorer renders your webpages. This topic describes document compatibility modes in Internet Explorer 10.
By default, pages are rendered in Internet Explorer 10 using the latest rendering engine. However, if the page's markup instructs the browser (via an "X-UA-Compatible" meta tag, a custom HTTP header from the web server, a !DOCTYPE declaration, or a combination of the three) to display it in an older document compatibility mode (for instance, IE9 Standards mode, EmulateIE7 mode, IE5 (Quirks) mode, and so on), Internet Explorer 10 displays the page in that compatibility mode. To learn more about compatibility modes, see Defining Document Compatibility on MSDN.
Internet Explorer 10 must be in IE10 Standards Mode to correctly display webpages that take advantage of the new features described in this document. The best way to ensure that Internet Explorer 10 renders your webpages using the latest rendering engine is to include the following !DOCTYPE declaration at the beginning of the page's HTML:
<!DOCTYPE html>
In addition, do not use an "X-UA-Compatible" meta tag on the page or send a custom HTTP header from the web server.
To force a webpage you are viewing in Internet Explorer 10 into a particular document compatibility mode, first open F12 Tools by pressing the F12 key. Then, on the Browser Mode menu, click Internet Explorer 10, and on the Document Mode menu, click Standards.