2011-07-21 IE9の過去のバージョンの互換モードで動作させるJavaScriptでも挙動が変わるものがある MSDN Internet Explorer 9 Compatibility Cookbookより参照 MIME types and plain text content (Windows) | Microsoft Docs Reducing MIME type security risks (Windows) | Microsoft Docs Enumerating JavaScript properties (Windows) | Microsoft Docs Math precision and SSE2 differences (Windows) | Microsoft Docs Array index handling (Windows) | Microsoft Docs