HTML - Navigating A Single Layer In Dhtml

<strong>Select: </strong><a href="#">video 1</a> | <a href="#">video 2</a> 
<div id="generic">generic page</div>
<div id="video1">vid1</div>
<div id="video2">vid2</div>

div { background-repeat: no-repeat; position: absolute; visibility: visible; }

#dropmenudiv{
position:absolute;
border:1px solid black;
border-bottom-width: 0;
font:normal 12px Verdana;
line-height:18px;
z-index:100;
}

#dropmenudiv a{
width: 100%;
display: block;
text-indent: 3px;
border-bottom: 1px solid black;
padding: 1px 0;
text-decoration: none;
font-weight: bold;
}

#dropmenudiv a:hover{ 
color:#000000;
background-color: #cc0000;
}

<script type="text/javascript">

var menu1=new Array()
menu1[0]='<a href="group.html">About (group)</a>'
menu1[1]='<a href="officers.html">Current Officers</a>'
menu1[2]='<a href="officerjoin.html">Become an Officer</a>'

var menu2=new Array()
menu2[0]='<a href="meetings.html">Meetings</a>'
menu2[1]='<a href="alumniday.html">Alumni Day</a>'
menu2[2]='<a href="industryday.html">Industry Day</a>'
		
var menuwidth='165px'
var menubgcolor='lightyellow' 
var disappeardelay=50  
var hidemenu_onclick="yes" 


var ie4=document.all
var ns6=document.getElementById&&!document.all

if (ie4||ns6)
document.write('<div id="dropmenudiv" style="visibility:hidden;width:'+menuwidth+';background-color:'+menubgcolor+'" onMouseover="clearhidemenu()" onMouseout="dynamichide(event)"></div>')

function getposOffset(what, offsettype){
var totaloffset=(offsettype=="left")? what.offsetLeft : what.offsetTop;
var parentEl=what.offsetParent;
while (parentEl!=null){
totaloffset=(offsettype=="left")? totaloffset+parentEl.offsetLeft : totaloffset+parentEl.offsetTop;
parentEl=parentEl.offsetParent;
}
return totaloffset;
}

function showhide(obj, e, visible, hidden, menuwidth){
if (ie4||ns6)
dropmenuobj.style.left=dropmenuobj.style.top="-500px"
if (menuwidth!=""){
dropmenuobj.widthobj=dropmenuobj.style
dropmenuobj.widthobj.width=menuwidth
}
if (e.type=="click" && obj.visibility==hidden || e.type=="mouseover")
obj.visibility=visible
else if (e.type=="click")
obj.visibility=hidden
}

function iecompattest(){
return (document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body
}

function clearbrowseredge(obj, whichedge){
var edgeoffset=0
if (whichedge=="rightedge"){
var windowedge=ie4 && !window.opera? iecompattest().scrollLeft+iecompattest().clientWidth-15 : window.pageXOffset+window.innerWidth-15
dropmenuobj.contentmeasure=dropmenuobj.offsetWidth
if (windowedge-dropmenuobj.x < dropmenuobj.contentmeasure)
edgeoffset=dropmenuobj.contentmeasure-obj.offsetWidth
}
else{
var topedge=ie4 && !window.opera? iecompattest().scrollTop : window.pageYOffset
var windowedge=ie4 && !window.opera? iecompattest().scrollTop+iecompattest().clientHeight-15 : window.pageYOffset+window.innerHeight-18
dropmenuobj.contentmeasure=dropmenuobj.offsetHeight
if (windowedge-dropmenuobj.y < dropmenuobj.contentmeasure){ //move up?
edgeoffset=dropmenuobj.contentmeasure+obj.offsetHeight
if ((dropmenuobj.y-topedge)<dropmenuobj.contentmeasure) //up no good either?
edgeoffset=dropmenuobj.y+obj.offsetHeight-topedge
}
}
return edgeoffset
}

function populatemenu(what){
if (ie4||ns6)
dropmenuobj.innerHTML=what.join("")
}


function dropdownmenu(obj, e, menucontents, menuwidth){
if (window.event) event.cancelBubble=true
else if (e.stopPropagation) e.stopPropagation()
clearhidemenu()
dropmenuobj=document.getElementById? document.getElementById("dropmenudiv") : dropmenudiv
populatemenu(menucontents)

if (ie4||ns6){
showhide(dropmenuobj.style, e, "visible", "hidden", menuwidth)
dropmenuobj.x=getposOffset(obj, "left")
dropmenuobj.y=getposOffset(obj, "top")
dropmenuobj.style.left=dropmenuobj.x-clearbrowseredge(obj, "rightedge")+"px"
dropmenuobj.style.top=dropmenuobj.y-clearbrowseredge(obj, "bottomedge")+obj.offsetHeight+"px"
}

return clickreturnvalue()
}

function clickreturnvalue(){
if (ie4||ns6) return false
else return true
}

function contains_ns6(a, b) {
while (b.parentNode)
if ((b = b.parentNode) == a)
return true;
return false;
}

function dynamichide(e){
if (ie4&&!dropmenuobj.contains(e.toElement))
delayhidemenu()
else if (ns6&&e.currentTarget!= e.relatedTarget&& !contains_ns6(e.currentTarget, e.relatedTarget))
delayhidemenu()
}

function hidemenu(e){
if (typeof dropmenuobj!="undefined"){
if (ie4||ns6)
dropmenuobj.style.visibility="hidden"
}
}

function delayhidemenu(){
if (ie4||ns6)
delayhide=setTimeout("hidemenu()",disappeardelay)
}

function clearhidemenu(){
if (typeof delayhide!="undefined")
clearTimeout(delayhide)
}

if (hidemenu_onclick=="yes")
document.onclick=hidemenu

</script>

<li><a href="events.html" onClick="return clickreturnvalue()" onMouseover="dropdownmenu(this, event, menu2, '150px')" onMouseout="delayhidemenu()">Events</a> </li>