Executive Summary:

IE 8.0 RC1 sports a major compatibility change plus added security and privacy changes. To accommodate enterprises, all of the new functionality added since Beta 2 is controllable via Group Policy, including the Compatibility View button and InPrivate Blocking. Developers will see better adherence to the Cascading Style Sheets (CSS) 2.1 and 3.0 specifications, as well as some new Developer Toolbar functionality.


Feedback about Microsoft's Internet Explorer (IE) 8.0 Beta 2 release prompted the company to add an unexpected release-candidate (RC) milestone to the IE 8.0 list, delaying the final release of the browser from late 2008 to the second quarter of 2009. Microsoft had released IE 8.0 Beta 1 in March 2008, aimed at developers, and IE 8.0 Beta 2 added end-user functionality. To learn more about IE 8.0 features, see “What You Need to Know About Microsoft Internet Explorer 8.0 Features. But it also added compatibility challenges, which Microsoft is addressing with IE 8.0 RC1. Here's what you need to know about late-breaking changes in IE 8.0.

Compatibility Issues
One of the biggest changes in IE 8.0 is the compatibility model. Microsoft is changing the browser’s core rendering engine to one that’s more standards-compliant, which means that eventually website designers and developers will need only to write to web standards, not the quirks of various browsers. But in the short term, this change has monumental negative effects because so many websites and corporate intranet sites are designed specifically for IE 6.0 and IE 7.0.

To combat the compatibility issues, Microsoft created a special Compatibility View button for the IE 8.0 toolbar. End users could toggle this button on websites that didn’t display properly in IE 8.0, and corporations could use IE 8.0's copious management capabilities to hard-code the backwards-compatibility mode for intranets and other sites. Microsoft also hoped that IE 8.0’s year-long beta period would give developers time to cope with the new rendering engine.

But few developers changed their sites in 2008 to work properly with the IE 8.0 rendering engine, and the Compatibility View button, while well-intentioned, put the onus of site compatibility on the end user. Clearly, Microsoft needed a more automated solution before IE 8.0 could ship to the public.

This solution, dubbed Compatibility View Updates, provides the browser with a constantly updated black list of sites known to not display properly in IE 8.0's default rendering engine. When the browser hits such a site, IE 8.0 switches automatically into Compatibility Mode. And when such a site is updated to handle IE 8.0, it’s removed from the black list automatically.

For those who don’t want this new functionality exposed in the browser, Compatibility View Updates is optional, easy to remove, and configurable in managed environments. And you can, of course, still manually add sites to Compatibility Mode when required.

UI, Privacy, and Security Changes
In addition to the major compatibility change discussed above, Microsoft has made other changes to IE 8.0 since the Beta 2 release. It removed AutoComplete Suggestions from the Address Bar but added the ability to show more previously visited or popular sites in the Address Bar drop-down menu. The new Favorites Bar, which replaces and enhances the Links Bar from previous IE versions, is more configurable as well.

IE 8.0's privacy and security functionality also changed. InPrivate Subscriptions, which blocked downloads and add-ons from specific sites, was removed. But the related InPrivate Blocking feature was changed so that all add-ons are disabled when browsing in this mode. InPrivate is also now session-specific, so that all new browser windows opened while in this mode will use InPrivate mode. (Previously, new windows would open in non-private IE mode instead.)

Enterprise and Developer Changes
To accommodate enterprises, all of the new functionality added since Beta 2 is controllable via Group Policy. This includes features such as the Compatibility View button and InPrivate Blocking.

Developers will see better adherence to the Cascading Style Sheets (CSS) 2.1 and 3.0 specifications, as well as some new Developer Toolbar functionality. For example, it's now possible to configure different text editors to work with the toolbar.

Recommendations
IE 8.0’s key end-user changes such as Accelerators, Web Slices, and Visual Search Suggestions make this version far more compelling than competing browsers such as Mozilla Firefox. The problem is that IE 8.0's new rendering engine could cause headaches for businesses that rely on quirks in earlier IE versions, so it's important to test your intranet and public websites in the new browser as soon as possible. The compatibility changes in the release candidate will help, but looking ahead, it’s advisable to migrate sites to web standards that work properly in all modern browsers.

The big question is whether IE 8.0’s functional improvements outweigh the compatibility issues and the pain of upgrading. Because IE 8.0 will be included in Windows 7, most businesses, I suspect, will simply "upgrade" to IE 8.0 as part of a Windows 7 migration, which seems like a more commonsense approach than upgrading existing Windows Vista and Windows XP machines to IE 8.0.