// array can contain object references, element ids, or both
var ids = ["nav-tier-1a", "nav-tier-1b", "nav-tier-1c", "nav-tier-1d", "nav-tier-1e", "nav-tier-1f"];

function hoverOn(e) { 
	document.getElementById(this.id + "-subnav").style.display = "block";
	document.getElementById(this.id).className= "nav-tier-1-list open";
	document.getElementById(this.id + "_link").className= "tier1 down";
}

function hoverOff(e) { 
	document.getElementById(this.id + "-subnav").style.display = "none";
	document.getElementById(this.id).className= "nav-tier-1-list";
	document.getElementById(this.id + "_link").className= "tier1";
}

YAHOO.util.Event.addListener(ids, "mouseover", hoverOn);
YAHOO.util.Event.addListener(ids, "mouseout", hoverOff);