Main web page in standard mode, iframe in compatibility mode: any issues?

Question

We have some legacy HTML content which we must render in compatibility mode. The requirement comes from our customers who want their HTML-based reports (some of which were c

Answer 1

As of IE9 mode, webpages cannot display multiple document modes. For example, consider a standards-based webpage that contains a frame element that displays content in quirks mode. IE9 mode displays the child frame in standards mode (because the parent document is in standards mode).

According to my tests, this is not true; my sample works as desired in IE9: the main page is in standard mode, the frame page is in quirk mode.

Not quite; when your sample works as desired it's actually displayed in a single display mode, with quirks mode emulated for the frame content. You shouldn't care about the underlying mechanics as long as the resulting output matches what you were after, although there is some anecdotal evidence of differences between emulated and native modes (mostly to do with js DOM manipulation).

I'd be a bit more concerned about how IE10+ would handle such fringe scenarios:

Starting with IE11 Preview, document modes are deprecated and should no longer be used, except on a temporary basis. Make sure to update sites that rely on legacy features and document modes to reflect modern standards.

Ninja edit: looks like this has already been resolved on SO; modifying the accepted solution to your needs you should omit Doctype and add ; X-UA-Compatibility correctly defined as per msdn spec