Center a div in the page

Not a CSS guru, but flexbox make it really easy

Method 1:

container use display:flex, and item use margin:auto

Method 2:

container use display:flex, justify-content:center, align-items:center. Here justify-content positions items in the main-axis of the flex(default in the row direction), and align-items positions items in the axis that is orthogonal to the main-axis