Are IE7 and 8 modes in IE9 the real thing?

Question

我只是想知道F12工具栏菜单中的IE7和IE8模式是否实际上使用IE7和IE8来呈现页面，如果它们与它们的独立对应物之间有任何差异？

Answer 1

There are differences. From my understanding, you really can't rely on them for JavaScript because IE9 will still use its IE9 JS engine, rather than the true ones from IE7 and IE8. And I'm sure even the rendering engines aren't 100% accurate.

In all my searching for the holy grail of IE testing, there only one thing that you can truly depend on: testing actually on a Windows OS running that browser. Microsoft offers a program called Virtual PC and provides downloads for virtual discs that contain different versions of Windows & IE.

If you really want accuracy, this is the only way to go.