This issue was raised against NetBeans IDE which is dependent on the composite.taglib.xml descriptors to be able to detect list of tags and their attributes per project.
<cc:clientBehavior> tag is used to add ajax support to composite components,
for more information:
Currently the tag is not recognized by the IDE, so it adds a red icon the the
project root indicating that the project contains files with errors. The
project runs without problems but the red icon remains.
Link to the related NetBeans issue: http://netbeans.org/bugzilla/show_bug.cgi?id=224768
Please complete the composite.taglib.xml file, thanks a lot.