QPushButton
{
    border:0px; 
    image: url(data/UI/images/known.png);
}
QPushButton:hover
{
    image: url(data/UI/images/known_hover.png);
}
QPushButton:pressed
{
    image: url(data/UI/images/known_down.png);
}
QPushButton:disabled
{
    image: url(false.png);
}