FAQ: CSS Display and Positioning - Z-Index


This community-built FAQ covers the “Z-Index” exercise from the lesson “CSS Display and Positioning”.

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This exercise can be found in the following Codecademy content:

Web Development

Learn CSS

FAQs on the exercise Z-Index

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why is the value of z-index is 10 here?


The number is arbitrarily higher than zero. It could be 1, or 100, or 1000 and not matter so long as it is higher than the element we are attempting to overlap. All elements have z-index = 0 by default.


Just curious, does codecademy have the fixed and absolute positioning rules backwards? It seems like the lesson was saying when the position of an element is set to absolute it should scroll with the user(when I did it, it didn’t do that), and when it is set to fixed, it should stay fixed on the page and not go with the scroll(which is what happened when I scrolled). I don’t know if I misunderstood the article or if the developers got it wrong. Who knows?


So the higher the z-index value is, it becomes the top???
What is the default z-index values of position fixed, absolute and relative?
Like if some elements overlap each other and with each one, they had position absolute or relative or etc, which one goes on top??


z-index applies to normal flow. How it applies to position: fixed and position: absolute will take some experimenting.

Yes, when elements overlap, the one with the higher z-index will appear on top. The default z-index value is, I believe, zero, or in general terms, no elements have the property.

When we have two elements that overlap, the one with a z-index property will likely be on top. Some experimenting will prove this out.

Save your experiments, both the HTML/CSS and a screenshot. Share your findings, please.