Select the warning/error, right click and choose "Quick fix" -> "Do
not use the WAR directory for YourProject launching and deploying
(this disables management of WEB-INF).". Click "Finish".
That will create a file ".settings/
com.google.gdt.eclipse.core.prefs" :
#Mon Nov 21 14:32:10 CET 2011
eclipse.preferences.version=1
warSrcDirIsOutput=false
Dominique.