vh & vw - sandrooliveira/advanced-css-course GitHub Wiki
This unit is really simple.
vh = x * 1% of the viewport height vw = x * 1% of the viewport width
The viewport is the user visible area of a page in the browser, so in the example below, the height of the header will be 90% of the screen and the widht 99%.
header { height: 90vh; width: 99vh; }