display: grid; justify-content: center; align-items: start; column-gap: 20px; grid-template-columns: 1fr auto 340px 1fr; grid-template-rows: 1fr 1fr; code example

Example 1: css grid

.item-a {
  grid-area: header;
}
.item-b {
  grid-area: main;
}
.item-c {
  grid-area: sidebar;
}
.item-d {
  grid-area: footer;
}

.container {
  display: grid;
  grid-template-columns: 50px 50px 50px 50px;
  grid-template-rows: auto;
  grid-template-areas: 
    "header header header header"
    "main main . sidebar"
    "footer footer footer footer";
}

Example 2: display grid

.container {
  display: grid | inline-grid;
}