How to specify QuirksMode for doctype in iframe in IE 9?

Question

Question:

We have a portal, where the doctype is compatible to xhtml 1.0. Then, in the portal, we have a content iframe, where we embed different web-applications. Some of those application were written by us, some are 3rd party.

Now in that iframe, we embed, amongst other things, Microsoft Reporting Service reports. The problem is, Reporting Service Reports requires QuirksMode to render "correctly". And the portal doesn't work in QuirksMode (which is fine, as far as I am concerned, since we only target 9, and possibly IE8). The portal also doesn't render fine in IE7, and we're going to abandon IE8 support as soon as possible.

However, IE9 seems to inherit the document mode from the parent page, so the reporting service reports gets rendered in IE9 standards mode instead of quirks mode. So all the reports are displayed incorrectly (and i don't mean a little bit, it's really severe, completely incorrect, absolutely horrible)

The problem is, we can't change reporting service...
There's no way to make reporting service (any version) render non-quirksmode HTML.

As per Will an iframe render in quirks mode? i could add

<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7">
<meta http-equiv="X-UA-Compatible" content="IE=8" />

To get the iframe to render in QuirksMode. (edit: doesn't even work when I don't care about how the portal renders and put it in anyway)

Unfortunately, the portal is as said, not IE7 compatible, so this is not an option.
Also, the SSRS reports runs on another domain than the portal, so I can't use JavaScript/jQuery in any way.

Is there any way to make an iframe render in QuirksMode, without destroying the parent page layout ?
Or a (already existing) way to make reporting service render valid HTML (I certainly don't have the time to write a custom HTML rendering extension) ?

Answer 1

Via MSDN:

Although the newer rendering engine is only used when Windows® Internet Explorer® detects that an HTML page has requested the highest level of support for standards, the same is not always true for child pages that might be loaded within frame and iframe elements. Because only one rendering engine can be active at a time, IE9 Mode also includes emulation for Quirks Mode.

Sorry, but what you want to do is impossible to achieve in IE9.