It could be handy to use the Ctrl+Shift+I shortcut for resolving (add missing, remove unused) namespace declarations in XHTML facelet page. Semantically it is similar action to e.g. adding imports in Java or uses in PHP.
But it would probably require also dialog where user can select proper namespaces if there are multiple choices :)
Thanks Vlado for the report. It's definitelly great idea and I think that users would appreciate that. Actually I found similar issue by creation of plans for NB80, so I'm marking this issue as a duplicate. But I believe that we will be implement this into next version.
*** This bug has been marked as a duplicate of bug 205232 ***