.QSS File Extension
What is a QSS file?
Style sheet file used by Qt (pronounced "cute") programs; contains definitions for the look and feel of GUI elements, including fonts, sizes, colors, layouts, and mouse-over behaviors; stores a library of styles that can be incorporated into a user interface.
Qt is a cross-platform development framework used to create applications in multiple environments without recompiling program code. It is used by Google Earth as well as VLC media player.
QSS files are similar to .CSS files. They can be created with any text editor.
NOTE: Qt SDK was previously developed by Nokia before Digia acquired the software.