Answers for "Which CSS property configures a grid container?"

responsive css grid

@supports (display: grid) {
  main { 
    max-width: 10000px;
    margin: 0;
  }
  .grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 2fr));
    grid-gap: 1rem;
  }
}

choose grid position html

/* grid-column: <start> / <end>;  */
/* grid-row: <start> / span <length>;  */
/* i.e */
grid-column: 3 / span 2;
grid-row: 2 / 4;
grid-row: 4;