The :active CSS pseudo-class matches when an element is being activated by the user. It allows the page to give a feedback that the activation has been detected by the browser. When interacting with a mouse, this is typically the time between the user presses the mouse button and releases it. The :active pseudo-class is also typically matched when using the keyboard tab key. It is frequently used on <a> and <button> HTML elements, but may not be limited to just those.
This style may be overridden by any other link-related pseudo-classes, that is :link, :hover, and :visited, appearing in subsequent rules. In order to style appropriately links, you need to put the :active rule after the all others link-related rules, as defined by the LVHA-order: :link — :visited — :hover — :active.

<!DOCTYPE html>
            a:active {
                color: #0F3
             /* active links */ 
                Click this link to see active effect
				<a href="#">will change on click</a>