css-grid.css

.grid {
    display: grid;
    grid-template-areas: 
        'header header header'
        'sidebar content content'
        'footer footer footer';
    column-gap: 20px;
}

.grid > .header {
    grid-area: header;
    height: 50px;
    background: #e6e5e5;
    padding: 10px;
}

.grid > .sidebar {
    grid-area: sidebar;
}

.grid > .content {
    grid-area: content;
}

.grid > .footer {
    grid-area: footer;
    height: 50px;
    background: #e6e5e5;
    padding: 10px;
}