This is a heading

Because the image has a z-index of -1, it will be placed behind the text.

Z-index Example

An element with greater stack order is always above an element with a lower stack order.

Black box (z-index: 1)
Gray box (z-index: 3)
Green box (z-index: 2)

Overlapping elements with no z-index

If two positioned elements overlap each other without a z-index specified, the elements render in the order they are defined in the HTML source code:

Black box
Gray box
Green box