How do I make a dynamic layer (Div) rather than an absolute one?

[Titus A Ducksass]

I want the effect of having a second layer (div) move relative to the
1st layer depending on the size of the font the user is using or if
the screen is resized so that the 1st layer does not over run the
second layer.

I can do this if I use tables for layout but cant figure it out for
layers.

 

[David Dorward]

I want the effect of having a second layer (div) move relative to the
1st layer depending on the size of the font the user is using

Define lengths in terms of the font size (em or ex units)

or if the screen is resized

Define lengths in terms of the canvas area (%ages)