Add a keyboard event listener to the element (keydown, keypress or keyup) which will trigger the same functionality as the mouse event.
Engine scans for element that uses one of the following events: click, dblclick, mousedown or mouseup, but has no corresponding keyboard event (keydown, keypress or keyup) on itself, on a child element up to level 3 down or on a parent element up to level 3 up.
Using both keyboard-specific and mouse-specific events ensures that content can be operated by a wide range of devices. For example, a script may perform the same action when a keypress is detected, same as, if it were clicked by a mouse.
<a href="menu.php" onmouseover="swapImageOn('menu')" onfocus="swapImageOn('menu')"