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My Employer does this also, all sites are our intranet switch IE into IE7 compatibility mode. Does matter if the need compatibility mode or not. We recently released a version of the web app I am building and I wish you couldve seen the horror on our faces when we saw the app in IE 7 mode.
Well, unless they actually change it in group policy, this is the default action for IE when it connects to anything on what it considers to be Intranet. You can override this by setting X-UA-Compatible to IE=edge as a HTTP header on your server. The equivalent meta tag is ignored in this situation. Or you could ask IT to change group policy, but I have no idea where that setting might live.
I believe we added this as a meta tag on the HTML pages, we didnt think of changing the HTTP header on the server.
I doubt they will be willing to change the IT group policy because the app we built has a smaller userbase than other apps. That and they are still supporting web apps from the late 90s - early 00s designed for IE 5/6.