Add some color to deviantART's header bar with HeaderCons! It has always somewhat bothered me that Messages is the only menu item accompanied by an icon, so I decided to create a user style that adds icons to all of them! This not only makes the menu look a whole lot more eye-candy, but boosts its usability as well, as each item becomes more easily recognizable.
To use this style, you'll need either Firefox or Chrome with the addon Stylish (for Firefox | for Chrome) installed. If that's the case, head over to this link and simply hit Install.
Not sure if I understood your question correctly, but are you asking why this only works for you and not for other deviants? Well, it's because this is a userstyle, meaning it doesn't change anything on deviantART itself, but only the way deviantART is displayed for the users that install it in their browser. So only the people that installed it will see the effect, not everyone.