Why Do CSS3 Transitions Not Work When Display Is Set To None?

CSS3 Transitions Not Working with Display Property

In CSS, the display property plays a critical role in defining whether an element is visible or hidden. Transitions, on the other hand, allow for smooth visual changes over time. However, attempting to apply transitions to elements with a display set to none can lead to unexpected behavior.

Addressing the Problem

The issue stems from the nature of the display property. When an element's display is set to none, it is removed from the page as if it were never there. As such, it cannot be partially displayed or undergo transitions.

Alternative Solution: Using Opacity

To achieve the desired fading effect on hover, consider utilizing the opacity property instead. Opacity controls the transparency of an element, allowing it to gradually appear or disappear.

CSS Solution

Implement the following CSS adjustments to enable the fading effect:

#header #button:hover > .content {
    opacity: 1;
    height: 150px;
    padding: 8px;
}

#header #button .content {
    opacity: 0;
    height: 0;
    padding: 0 8px;
    overflow: hidden;
    transition: all .3s ease .15s;
}

By combining opacity and transition, the hidden content fades into view when hovering over the button. Vendor prefixes for cross-browser compatibility have been omitted for brevity.

Other Considerations

Apart from opacity, one could also explore adjusting the height and padding properties to achieve similar effects.

Additional Resources

• [CSS Transitions Tutorial](https://www.w3schools.com/css/css3_transitions.asp)
• [Handling Hidden Elements with CSS Transitions](https://css-tricks.com/transitions-with-hidden-elements/)
• [Similar Topic on Stack Overflow](https://stackoverflow.com/questions/30130725/css-animation-not-visible-when-display-none)

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