I need some help with the z-index.

Question

Im placing the z-index: -1; for the gray contentBox but its not doing something. Im trying to get the contentBox behind the form.

Answer 1

The code you mentioned is not in your code playground.
Please share your code by posting a link here.

Answer 2

z-index can be very tricky and might have different result with differents web browsers. I personnaly prefer never use that CSS attribute and prefer to change orders of HTML tags directly in the DOM structure, which will naturally change Z axe from HTML elements.