Control Document Mode in an HTML Application

HTML applications, by default, display webpages in Compatibility View, which displays standards-mode content in IE7 Standards mode and quirks mode content in IE5 (Quirks) mode. This means that you cannot use post-IE7 features such as JSON.stringify(), or expect standards-compliant CSS support, unless you add the following code to your HTML application(HTA):

<meta http-equiv="X-UA-Compatible" content="IE=9" />

Where IE=9 can be replaced with IE=8, IE=10, or even IE=edge to automatically choose the most up-to-date document mode supported by the version of Internet Explorer installed on your machine.

Sources:

• "Introduction to HTML Applications (HTAs)", MSDN
• "Specifying legacy document modes", MSDN