function hideMedia(obj){
	document.getElementById(obj).style.visibility = 'hidden';	
}
function showMedia(obj){
	document.getElementById(obj).style.visibility = 'visible';	
}

function imageOver(obj){
     var srcName = obj.src;
     obj.src = srcName.replace("-off.","-on.");
}
function imageOut(obj){
     var srcName = obj.src;
     obj.src = srcName.replace("-on.","-off.");
}