function showDisplay(id,display) { 
document.getElementById(id).style.display=display; 
} 
function showHide(id,vis) { 
document.getElementById(id).style.visibility=vis; 
} 
// <p><a href="#" onmouseover="showHide('Layer3','visible')" onmouseout="showHide('Layer3','hidden')">Mouse me!</a> </p> //
// <p><a href="#" onmouseover="showDisplay('Layer4','block')" onmouseout="showDisplay('Layer4','none')">Mouse me too!</a> </p> //