As I was reading Ajax in Action by Dave Crane, Eric Pascarello, in Appendix A they discuss Editors and IDEs for web development. Apparantly, the authors didn't get the message than IDEA 5.0 supports web languages.
"Integrated development environments
Enterprise programming launguages such as .NET and Java have a long history of integrated development environments. The market for these is mature, and in recent years, a number of mature feature-rich open source and freeware IDEs have appeard. IDEs designed for server-side coding languages are often extensible enough to allow for client-side development using Ajax.
Some enterprise Java development tools such as the Sun Java Studio Creator and SAP NetWeaver offer high-level design facilities for web applications. IN our experience, these are based heavily on the classic web application metaphor, with an application being modeled as a series of discrete pages, and may translate poorly to the Ajax approach. Studio Creator uses Java ServerFaces (JSF) behind the scenes, however. We discussed JSF and Ajax in Chapter 5, and although the two technologies have some challenges to overcome before being fully interoperable, it may be possible that JSF-based tools with support Ajax better in the near future.