.gird{
    display:grid;
    grid-template-columns:1fr 1fr 1fr;
    grid-gap: 10px;   
    
}

.cell{
    background-color: rgb(220,220,220);
    height: 100px;
    
}

header{
    grid-column: 1/4;
    grid-row: 1;
    height: 300px!important;
    
}
nav{
    grid-column: 1/4;
    grid-row: 2;
    height: 30px!important;
}
aside{
    grid-column: 1;
    grid-row-end: span 2;
    height: auto!important;
    
}
footer{
    grid-column-end: span 3;
    grid-row-end: span 2;
}