What Happens to Absolutely Positioned Elements with No Explicit Top, Left, Bottom, or Right Values?

Understanding Default Position Values for Absolute Positioning

In CSS, when an element is positioned absolutely, its coordinates are specified relative to its containing block. However, what happens when no explicit values are provided for the top, left, bottom, or right properties? To unravel this mystery, let's examine the default values and their implications.

As expected, the default value for all these properties is not zero, but rather "auto". According to the CSS specification (Section 9.3.2), when all offsets are set to auto for an absolutely positioned box, it remains in its original position as if it were not positioned at all.

This concept becomes clearer in Section 10.3.7 of the spec, which dictates that when all three of left, width, and right are auto, the left property is resolved first. If the element's directionality is left-to-right ('ltr'), left is set to the static position; otherwise, right is set to the static position

Similarly, Section 10.6.4 governs vertical dimension constraints for absolutely positioned elements. If top, height, and bottom are all auto, the top property is assigned the static position by default.

In practical terms, this means that an absolutely positioned element without any explicit coordinate values will remain where it would have been normally positioned, without any shifts in its location. This is known as the "static position".

To summarize, when no specific values are specified for the top, left, bottom, or right properties of an absolutely positioned element, they assume the default value of auto, which effectively retains the element's original position within its container.

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