Thread:Project:Support desk/No Notification tab in preferences

Mediawiki-1.23.5 is installed

the wikisysop send a bienvenue message to a new user.talk page the new user see an orange bar given him a notification but this notification cannot be removed.... it always appears on each page

my installation doesn't give a preference notification tab ? there is no red icon with a notification number next to user name as on this wiki

What I have forgotten to installed ? Thanks for your answering