Is there a way to disable compatibility mode in IE8, if already enabled?

Question

I'm "sunsetting" the IE7 support for a web app, and I don't want IE8 users to see an "oops, you are using an old browser" warning.

If an IE8 user has already clicked the compatibility mode button, is there a way for a web page to immediately disable the compatibility mode? Setting the X-UA-Compatible header or meta tag doesn't seem to help.

I found an blog post (!) about adding an IEStandards.xml, but even that solution would not have immediate results: the xml file is reportedly polled by IE8 only once every 30 days. Another blog post lists the options for a site to be removed from the list, and that does not give me more hope.

(IE9 is different. Even if the user has set the compatiblity mode earlier, it seems to disable it, if given the correct X-UA-Compatible header and/or meta tag. This is documented.)

Answer 1

I ended up just detecting the compatibility mode and then nagging the user. At least Google Plus does this.