.body-grid{
    display: grid;
    grid-template-columns: 15% 70% 15%;
    grid-template-areas: 'left-side main-section right-side'
    'footer footer footer';
}

.left-side{
    grid-area: left-side;
}
.main-section{
    grid-area: main-section;
}
.footer{
    grid-area: footer;
}