.master {
display: grid;
grid-template-columns: repeat(3, 1fr);
grid-template-rows: repeat(3, 1fr);
grid-column-gap: 0px;
grid-row-gap: 0px;
}

html, body
{
    height: 100%;
    width: 100%;
}



.haut { grid-area: 1 / 1 / 2 / 4;width:100%;height:100%;min-height: 100px; }
.bas { grid-area: 3 / 1 / 4 / 4;width:100%;height:100%;min-height: 100px;text-align:center;}
.gauche { grid-area: 2 / 1 / 3 / 2;width:100%;height:100%;min-width:100px; }
.droit { grid-area: 2 / 3 / 3 / 4;width:100%;height:100%;min-width:100px;}
.centre { 
grid-area: 2 / 2 / 3 / 3;;i
width:100%;height:100%;
min-width:100px;
text-align:center;
margin:15px;
padding:15px;
}

.haut > div {
float:left;
width:20%;
text-align:center;
margin:15px;
padding:15px;
}