[cager]

Recently I am getting epub books which the Editor Check Book is giving red warnings for invalid CSS 2.1 when the property is like
height: 100vh;

I understand that this is a new measurement unit in CSS3.

I am converting the epub to AZW3 for a basic Kindle.

Do I:
1. Ignore;
2. Delete the line so there is no reported error;
3. Change the 100vh to something else?