Quirks Mode, IE7 Mode, IE8 Mode, IE9 Mode, IE10 Mode, and IE11 Mode (All Versions)
Determines whether the content of the frame is an HTML Application (HTA), which is exempt from the browser security model.
Can be one of the following values:
yes– All content of the frame or iframe is trusted.
no– Default. Browser security rules for unsafe content are applied.
This attribute is available in markup only for frame and iframe elements.