The preview release is available for free download to anyone, but is intended for Web site and application developers who want to get an idea where the final product is headed. Microsoft also is hoping to collect feedback on the browser and its new feature from those developers.
Microsoft detailed and demonstrated the new features at the recent TechEd conference in New Orleans. Key developments in version 5.0 relate to the implementation of Dynamic HTML, or DHTML. DHTML refers to a set of Web building specifications including HTML, cascading style sheets (CSS), and scripting languages.
"When we came out with IE 4, applications developers were really interested in development functions with DHTML," said IE product manager Craig Beilinson. "And they gave us a ton of feedback on ways it could be easier and faster to use those things."
New features of the browser include:
Web development technologies are works in progress, and the World Wide Web Consortium (W3C), of which Microsoft and its competitors are members, has not yet recommended or in some cases even evaluated many of the technologies contained in next-generation browsers, including IE 5.
This lack of standardization on specific features could wreak havoc with Web surfers using competing or older browsers.
W3C officials advise developers to use caution before implementing the latest features.
"Developers can start to do things that appear in some new browser, but right away they should be aware that if it's proprietary, there's a risk of incompatibility," said W3C working group member Ian Jacobs. "They should try to do just standards-based development, but that may not get them the results they want.
"Accessibility may not be compatible with the coolest site you can build," he added. "That's a dilemma that will never go away, because every company wants to get an edge and develop their technology before anyone else."
Microsoft, for its part, contends that all the technologies that go into IE 5 have either been approved by or sent to the W3C for consideration. Microsoft's Beilinson also defended the process of implementing technologies without waiting for an official W3C recommendation.
"One of the nice things about how this is going to work is that developers will work on this in the real world, and they can give Microsoft and the W3C concrete feedback on what does and doesn't work," Beilinson said. "All this real-world feedback will make the final spec the most reliable that it could be."
A beta version of the browser is expected this summer.