CSS outline Property
The css outline property is a shorthand property for setting one or more of the individual outline properties outline-style, outline-width and outline-color in a single rule. In most cases the use of this shortcut is preferable and more convenient. Outlines differ from borders in the following ways: 1. Outlines do not take up space, they are drawn above the content. 2. Outlines may be non-rectangular. They are rectangular in Gecko/Firefox. Internet Explorer attempts to place the smallest contiguous outline around all elements or shapes that are indicated to have an outline. Opera draws a non-rectangular shape around a construct.