css tutorial

Question

hey guys
I have a problem with understanding this z-index's function and what is it doing exactly
can some one explain it better and simple
and about margin-left/right What is this?

Answer 1

Adding to Bagon's answer those elements should be positioned absolutely ,fixed or relatively

Margin-left and margin-right specifies the space between two elements or around a element ,

Answer 2

Basically objects with higher z-index will appear on top while lowers are behind