MediaWiki 1.22wmf2 on the English Wikipedia, Extension:Echo
(Bug added at the suggestion of [[User:MZMcBride]]; see http://en.wikipedia.org/wiki/Wikipedia_talk:Notifications#Allow_CSS_customisation_of_.22.281.29.22.)
I had the new notification indicator "(1)" at the top of my browser on Wikipedia for several hours without realising it. Hence I wanted to do something to make it more prominent; my first thought was user CSS. However, I looked at the HTML source and couldn't see a class= or id= to indicate new notifications.