问题
I just received a new computer at work, with IE8 set to render all sites as IE7. This was a shock to me. Does anyone know if ALL installations of IE8 default to IE7 rendering? And if so, is there anything a web developer can do to force IE8 rendering?
回答1:
As I know by default IE8 renders only intranet sites as IE7. To disable this go to Tools -> Compatibility View Settings and uncheck "Display intranet sites in Compatibility view". Also there is a checkbox "Display all sites in Compatibility view" in this dialog - it looks like it's checked for you. It's not standart setting, maybe it is your domain policy.
Anyway, if you need to force IE8 to render pages as IE8 use X-UA-Compatible http header. You can add meta tag in a head section of your page, like this:
<meta http-equiv="X-UA-Compatible" content="IE=8" />
MSDN
来源：https://stackoverflow.com/questions/4457851/ie8-rendering-as-ie7-by-default