Many Web Desingers want to reduce the base font size from 16 pixels to something smaller

Hello world. This is 16 pixels. Looks fine to me. This looks to big to many web designers for a base font size.

This is 14 pixels. We've now changed the base font of this page to 14 pixels by setting the font size to 62.5% on the body, thus making our 16 pixels 14 pixels.

The problem with this technique is the cascade / inheritance / compounding issue hence nested elements need to have thier size either calculated requiring tricky maths, or declared