Summary  
This chapter covers how to use the CSS z-index property to control the stacking order of positioned elements by assigning integer values, with higher values bringing elements to the front and equal values falling back to source order.

General domain of usage  
Front-end web development

The `z-index` property determines the stacking order of positioned elements on a web page. It only applies to positioned elements, which have a position value of `absolute`, `fixed`, `relative`, or `sticky`. As the elements are taken out of the normal document flow, to determine which of these positioned elements should be displayed higher or lower, we specify `z-index`.
```css
z-index: number_without_units
```

The higher value the `z-index` property has, the higher the element is shown on the user screen.

Let's practice. We have four `div` elements with the `box` class, each styled as a square and numbered to represent their order in the `html` document. The squares are currently positioned on top of each other. The task is to adjust the z-index property with the correct values to bring square 3 to the front and send square 4 to the back.

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>Note
>
>If we set the same value for the `z-index` property to different elements, the browser will show the elements in the order in which the elements are in the `html` file.

What is the purpose of the `z-index` property?

Level up your styling skills by mastering advanced CSS techniques for modern web design. Position and manage elements with precision using advanced positioning strategies. Create smooth transitions and engaging animations to enhance user experience. Transform and manipulate elements for dynamic visual effects. Build responsive designs that adapt across devices and learn to streamline your workflow with CSS preprocessors like Sass.

Research what learners can expect from this advanced HTML and CSS styling course. What do you need to know before starting the course? What topics will be covered in it?

Position and manage elements on the web pages. Learn about the different positioning properties, discover how to use the stacking order to control the visibility of elements that overlap each other, and finally, handle content overflow. 

Research the power of transitions and learn how to improve the user experience. Discover how to liven properties smoothly and gradually, creating seamless state transitions.

Learn about the animation property and how it can be used to create dynamic and engaging designs. Discover how to create complex animations using keyframes and how to control the animation.

Explore the transformation property, which allows modifying the appearance and position of elements on a webpage. Learn how to scale, rotate, skew, and translate elements in two and three dimensions. Combine multiple transformations to create more complex effects.

The principles and techniques used in adaptive/responsive design aim to make websites and applications accessible and visually appealing across different devices, screen sizes, and orientations.

Learn about preprocessors in CSS and how they can help to write more efficient and maintainable code. Understand how to use preprocessors to simplify the workflow and generate cleaner CSS code.

Managing the Stacking Order of Elements