How to setup the parallax effect
The class that triggers the parallax effect is
".rellax" and can be used to any other elements where you want to add a parallax effect.
<div class="rellax rellax-first" data-rellax-percentage="0.9" style="background-image: url('images/parallax-background.jpg');"> </div>
The code for js that changes the speed of parallax is found in