@media all and (min-width: 940px) {
    header h1 {
        color: #fff;
        text-shadow: none;
    }
    header {
        background-image: url('https://visuels.l214.com/sites/don.l214.com/2020/06-enq-roquefort/ban-desktop.jpg') !important; 
    }
}
@media all and (max-width: 700px) {
    #formulaireDon {
        background-image: url('https://visuels.l214.com/sites/don.l214.com/2020/06-enq-roquefort/ban-mobile.jpg') !important;
    }
}