The negative z-index keeps it below the content. Negative z-index is a fun trick, but beware this table then can’t be nested within other elements with backgrounds, otherwise the highlight will go below them. You can see that in action here: See the Pen

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Changing the Image URL. The red-colored texts shown in step #5 HTML code are the links of the pictures that you want to insert on the web page. To acquire the URL of the image, you would need to upload your picture to an image hosting site such as Flickr,