I live in the bowels of a big corporate, where I am adding a component to their very large intranet site. Each page contains a number of iframes, each hosting a component (the user can switch between the iframes using custom tabs).
Recently, it was decided to upgrade all employee computers from IE8 to IE9 (yes, this is 2014) - raising hopes that I could target IE9 for my component (a big improvement over IE8). However, it turns out that the other components (in other iframes) use IE8 specific functionality, and do not work in IE9. Those things are huge and conversion to standard compliance won't be done within a year.
For the iframes with content that only works in IE8, we include in the head, to switch IE9 to IE8 document mode.
Problem is that when I add in my iframe to allow me to target IE9, it stays in IE8 doc mode. I haven't been able to find a way to mix IE8 and IE9 mode in one page (even though the IE8 and IE9 bits sit in different iframes). If I can't solve this, I'll have to target IE8, which will be painful.
Is there a way in IE9 to have a page with iframes where some iframes use IE8 standard mode and others IE9 standard mode?
Nope, unfortunately there isn't. The browser mode is set according to the topmost frame's settings and all nested frames use the same mode.