When importing an eclipse based WSAD web project IDEA creates a Java Module instead of a web module. Its really not that hard to import it, there is a .websettings file which looks as follows.
Also it would really be great if IDEA could import a WSAD project team set file (.psf) as well.
<?xml version="1.0" encoding="UTF-8"?>
<websettings version="500">
<project-type>J2EE</project-type>
<context-root>ws</context-root>
<jsp-level>JSP 1.2</jsp-level>
<features>
<feature>
<feature-id>WebProjectCSSFileFeature</feature-id>
</feature>
</features>
<lib-modules>
<lib-module>
<jar>WSC_ClientSearch.jar</jar>
<project>WSC_ClientSearch</project>
</lib-module>
<lib-module>
<jar>WSS_ClientSearch.jar</jar>
<project>WSS_ClientSearch</project>
</lib-module>
</lib-modules>
<webcontent>WebContent</webcontent>
</websettings>