When you’re using Ubuntu, you’re using a set of buttons and on-screen controls (a ‘toolkit’) called GTK. Part of Linux’s strength is that there are many options to choose from in terms of toolkits and programming languages that can be used. The price for that is that these toolkits technically look a little different from each other. One of the easiest things to fix is how the QT toolkit looks. Open Ubuntu Software Center and search for qtconfig. One of the results will be QT4 Settings. Install that and when it’s finished, launch the app QT 4 Settings.
At the top of the Appearance tab, you’ll see the GUI Style section. Select the GTK+ style, then go up to File > Save, then File > Exit. Now QT4 apps will default to look like the rest of Ubuntu!