Application Compatibility and Deployment Guidance
Organizations that move from the Microsoft® Windows® XP operating system to Windows 7 are also moving their applications and websites from Microsoft Internet Explorer® 6 to Windows Internet Explorer 8. Getting these applications and websites to work on Internet Explorer 8 or Internet Explorer 9 may require some investment. Microsoft has published the white paper Addressing Application Compatibility when Migrating to Internet Explorer 8 to provide guidance for this effort. Customers who are interested in deploying Internet Explorer 9 should review the Internet Explorer 9 Deployment Guide.
That investment carries forward when moving from Internet Explorer 8 to Internet Explorer 9. In general, applications and websites that work in Internet Explorer 8 will continue to work in Internet Explorer 9. Likewise, applications and websites that work in earlier versions of Internet Explorer, but do not work in Internet Explorer 8, will also not work in Internet Explorer 9. The migration from Internet Explorer 8 to Internet Explorer 9 is expected to be easier than the migration from Internet Explorer 6 to Internet Explorer 8.
The high degree of compatibility from Internet Explorer 8 to Internet Explorer 9 is largely enabled by the Compatibility View feature. Compatibility View is on by default for intranet websites in Internet Explorer 8, and will work the same way in Internet Explorer 9. Compatibility View mode allows websites that were designed for Windows Internet Explorer 7 to work properly in Internet Explorer 8 and Internet Explorer 9. As a result, enterprises with intranet line-of-business (LOB) applications should not need to retest all applications when migrating from Internet Explorer 8 to Internet Explorer 9.
Enterprises with LOB applications running on an extranet or Internet site (that is, site URLs with a fully-qualified domain name) will also be able to carry forward application compatibility investments. You should use Group Policy, the X-UA-Compatible tag, or the http header to do so. Extranet or Internet LOB applications that work in Internet Explorer 8 standards mode will continue to work Internet Explorer 9, if Internet Explorer 8 document mode is specified using the X-UA-Compatible tag or http header. Similarly, extranet or Internet LOB applications that work in Internet Explorer 7 standards mode will continue to work in Internet Explorer 9. You must specify Internet Explorer 7 document mode, using the Internet Explorer 7 mode (Compatibility View) Group Policy or the X-UA-Compatible tag or http header. For more information about how to future-proof your applications by specifying legacy document modes, see Defining Document Compatibility.
In addition to tagging sites using X-UA-Compatible, to maximize ongoing application compatibility investments, LOB site owners should follow best practices for interoperability. For more information, see the Internet Explorer 9 Compatibility Cookbook.
We recommend that organizations who have just started their Windows® 7 and Internet Explorer® 8 migration planning, or are currently in the application testing phase of their Windows 7 and Internet Explorer 8 migration projects, switch to testing, piloting and deploying Windows 7 and Internet Explorer 9.
For organizations that are currently deploying Windows 7 and Internet Explorer 8, we recommend that they continue with these deployments. This will allow organizations to realize the benefits of Windows 7 and Internet Explorer 8 immediately. In parallel, we also recommend that these organizations pilot Internet Explorer 9 and make Internet Explorer 9 part of their longer-term desktop strategy.