How can you hide an element in HTML using CSS?

Hiding an element in HTML using CSS can effectively be achieved by setting the display property to none. When you use this property, the element is completely removed from the document's flow, meaning that it will not take up any space on the page. This results in the element not being visible and also not affecting the layout of any surrounding elements.

The display property controls the overall box model of the element, so when it's set to none, the browser will not render that element at all, providing a clean way to hide content.

In contrast, while setting the opacity property to 0 makes an element invisible, it still occupies space on the page. Similarly, setting the visibility property to hidden will make the element invisible but it continues to take up space as well. Using a negative z-index can move an element behind others but does not hide it, as it remains rendered on the page. Hence, setting the display property to none is the most effective way to hide an element in terms of layout and rendering.