For the gaming test, let's add a player for see the parallax performance on web browser.
Add a new layer and rename it as Main (block other layers for avoid problems).
Add the sprite you like and give him the Platform and ScrollTo behaviors.
Add a ground and make it invisible (select sprite- properties- Initial visibility-Invisible), also give it a width of 6000 and adjust it to the start of the window. Don't forget to give it the solid behavior.
Then press F5 and test your parallax effect.....
I hope you enjoyed this tutorial as much as I enjoyed to write it, soon I will make more tutorials with this example, don't forget to comment.
You can download the example files attached on "Tutorial Downloads" section.