An outline is a line that is drawn around elements (outside the borders) to make the element "stand out".
However, the outline property is different from the border property.
The outline is not a part of an element's dimensions; the element's total width and height is not affected by the width of the outline.
All CSS Outline Properties
The number in the "CSS" column indicates in which CSS version the property is defined (CSS1 or CSS2).
|outline||Sets all the outline properties in one declaration||outline-color
|outline-color||Sets the color of an outline||color_name
|outline-style||Sets the style of an outline||none
|outline-width||Sets the width of an outline||thin