What is the default value of the padding property if not specified for an element?

The default value of the padding property in CSS, when not specified, is indeed 0px. This means that if a padding value is not explicitly set for an element, it will not have any space added inside its border, effectively leading to no padding. The reason for this default behavior is to ensure that elements start with no space and provide a clear layout unless the designer decides to add some padding for styling purposes.

This default value allows for flexibility in design, as it gives developers the option to control the visual spacing around content. Other values like 'auto' and 'initial' serve different purposes and are not applicable in this context; 'auto' is usually used for properties where the browser needs to calculate a value based on the surrounding elements, and 'initial' sets the property to its default value specified by the CSS specification, which in the case of padding is also 0px.