Links to more advanced (and more recent) methods for CSS grids and positioning elements with CSS.

The CSS Grid

Information and Tutorial Videos are available on Rachel Andrew's site.

Article about choosing to work with CSS Grid or/and Flexbox

Video about working with CSS Grid

Flexbox

Complet Guide to Flexbox

Flexbox basics explained on the W3schools website.

Another Article about Flexbox

Video tutorials for Flexbox