Microsoft is calling on developers to ensure applications and websites are compatible with IE7 RC1 (Internet Explorer 7.0 Release Candidate 1.0) for Windows XP, which the company will make available later today.

RC1 means IE 7.0 is nearly ready for the prime time. IE 7.0 RC1 for Windows XP is a feature-complete version of the browser that is expected to be released in its final form in the final quarter of the year, said Margaret Cobb, group product manager for the IE team at Microsoft.

She called IE7 RC1 for Windows XP a 'call to action' for Microsoft's developer community, who can use the public release to ensure compatibility between the browser and applications so there will be no snags when IE7 is in its final release.

Microsoft added one new feature between IE7 for Windows XP's beta 3.0, which was released on 26 June, and RC1, Cobb said. The company added an auto-uninstall feature due to demand from testers who had to manually uninstall previous test versions of IE7 through Windows' Control Panel. "This simplifies the installation process," she said.

IE7 RC1 for Windows XP is available in two more languages than its previous test release. Microsoft has added French and Spanish options for the browser. IE7 for Windows XP beta 3.0 was available in English, German, Japanese, Arabic and Finnish. The final version of IE7 for Windows XP will be available in 35 languages, Cobb said.

IE7 for Windows XP is a 'subset' of the version of IE7 that will be included as part of Windows Vista, the next version of Microsoft's client OS. Vista's version of IE7 will contain two additional security features – protected mode and parental controls – than the version of the browser that will be available for Windows XP, Cobb said.

Once IE7 for Windows XP is in its final release, it will be available both as a free download from Microsoft's website, and through Microsoft's Automatic Updates service. However, Microsoft will give enterprises a tool that enables corporate desktops bypass the update if they so choose.

Some of the new features available in IE7 include built-in support for RSS feeds, tabbed browsing and improved security, including an antiphishing filter.

While IE is still the dominant web browser, Microsoft hopes with IE7 to win back some browser market share it's lost to Mozilla's open-source Firefox browser, which has grassroots appeal. According to NetApplications, a maker of applications for monitoring and measuring website usage, Firefox had 8.1 percent market share in July, while IE had 87.2 percent market share.