That's a question of zIndexing. The following will work. I left your original file intact as much as possible, but I had to correct quite a few errors. Also, I had to remove some styles in order for this post not to exceed the allowed length.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" >
<title>ddr4</title>
<style type="text/css">
body {font-family: verdana; font-size:12px; color: #333; background-color:#ccc; text-align:center;}
#video_container, #hider1, #hider2
{position:absolute; left:50%; top:50%; margin-top:-170px; margin-left:-310px; width: 550px; height:300px; overflow:hidden;}
#hider1, #hider2{background:black;color:white; display:none;}
#hide_button{position: absolute; left: 50%; top:50%; margin-top:-170px; margin-left: 225px; display: none; z-index:2; font-family: verdana; font-size: 12px; cursor: pointer; font-weight: bold; background: black; color: white}
ul.semiopaquemenu{ /* main menu UL */
font: normal 13px Georgia; width: 600px; background: #98A877; padding: 5px 0 5px 0; margin: 0; text-align: left; border:#444444 1px solid;
}
ul.semiopaquemenu li{display: inline;}
ul.semiopaquemenu li a {color:#444444; cursor:pointer; padding: 4px 8px 4px 8px; text-decoration: none; margin-left: 10px; border-left:#98A877 1px solid; border-right:#98A877 1px solid;}
ul.semiopaquemenu li a:hover, ul.semiopaquemenu li a.selected3 {color: #000000; background: url(http://i46.tinypic.com/rc99n5.jpg); border:#444444 1px solid; padding-top: 12px; padding-bottom: 12px;
}
div#kontejner { text-align:left; }
div#footer { text-align:center; }
div#kontejner { width:800px; margin:0 auto; background-color:#fff;border:#6E6E6E 1px solid; margin: 40px;margin-left:100px;margin-top:200px;}
div#blog { float:left; width:780px; padding:10px 0; margin-left:20px;}
</style>
<script type="text/javascript">
/*Contractible Headers script-Dynamic Drive (www.dynamicdrive.com)
This notice must stay intact for legal use. Last updated Mar 23rd, 2004.
Visit http://www.dynamicdrive.com/ for full source code*/
var enablepersist="on" //Enable saving state of content structure using session cookies? (on/off)
var collapseprevious="no" //Collapse previously open content when opening present? (yes/no)
if (document.getElementById){
document.write('<style type="text/css">')
document.write('.switchcontent{display:none;}')
document.write('<\/style>')
}
function getElementbyClass(classname){
ccollect=new Array()
var inc=0
var alltags=document.all? document.all : document.getElementsByTagName("*")
for (i=0; i<alltags.length; i++){
if (alltags[i].className==classname)
ccollect[inc++]=alltags[i]
}}
function contractcontent(omit){
var inc=0
while (ccollect[inc]){
if (ccollect[inc].id!=omit)
ccollect[inc].style.display="none"
inc++
}}
function expandcontent(cid){
if (typeof ccollect!="undefined"){
if (collapseprevious=="yes")
contractcontent(cid)
document.getElementById(cid).style.display=(document.getElementById(cid).style.display!="block")? "block" : "none"
}}
function revivecontent(){
contractcontent("omitnothing")
selectedItem=getselectedItem()
selectedComponents=selectedItem.split("|")
for (i=0; i<selectedComponents.length-1; i++)
document.getElementById(selectedComponents[i]).style.display="block"
}
function get_cookie(Name) {
var search = Name + "="
var returnvalue = "";
if (document.cookie.length > 0) {
offset = document.cookie.indexOf(search)
if (offset != -1) {
offset += search.length
end = document.cookie.indexOf(";", offset);
if (end == -1) end = document.cookie.length;
returnvalue=unescape(document.cookie.substring(offset, end))
}}
return returnvalue;
}
function getselectedItem(){
if (get_cookie(window.location.pathname) != ""){
selectedItem=get_cookie(window.location.pathname)
return selectedItem
}
else
return ""
}
function saveswitchstate(){
var inc=0, selectedItem=""
while (ccollect[inc]){
if (ccollect[inc].style.display=="block")
selectedItem+=ccollect[inc].id+"|"
inc++
}
document.cookie=window.location.pathname+"="+selectedItem
}
function do_onload(){
uniqueidn=window.location.pathname+"firsttimeload"
getElementbyClass("switchcontent")
if (enablepersist=="on" && typeof ccollect!="undefined"){
document.cookie=(get_cookie(uniqueidn)=="")? uniqueidn+"=1" : uniqueidn+"=0"
firsttimeload=(get_cookie(uniqueidn)==1)? 1 : 0 //check if this is 1st page load
if (!firsttimeload)
revivecontent()
}}
if (window.addEventListener)
window.addEventListener("load", do_onload, false)
else if (window.attachEvent)
window.attachEvent("onload", do_onload)
else if (document.getElementById)
window.onload=do_onload
if (enablepersist=="on" && document.getElementById)
window.onunload=saveswitchstate
</script>
<script type="text/javascript">
function include_video_prep(url)
{
video='<object id="the_video" type="application/x-shockwave-flash" style="position:absolute;width:100%;height:100%;" data=\''+url+'&vq=large\'><param name="movie" value='+'"'+url+'"'+'><param name="allowFullScreen" value="true"><param name="flashvars" value="autoplay=1"><param name="wmode" value="transparent"><param name="allowNetworking" value="all" ><param name="allowscriptaccess" value="always"><\/object>'
setTimeout("document.getElementById('video_container').innerHTML=video",0);
}
function include_video(which)
{
document.getElementById('hide_button').style.display='block';
document.getElementById('hider1').style.display='block';
document.getElementById('hider2').style.display='block';
document.getElementById('video_container').style.background='black';
document.getElementById('video_container').style.color='white';
document.getElementById('video_container').style.zIndex=1;
include_video_prep(which);
setTimeout("document.getElementById('hider1').style.display='none'; document.getElementById('hider2').style.display='none'",0);
}
</script>
</head>
<body>
<div id="kontejner">
<div id="zaglavlje"></div>
<div id="blog">
<div id="hide_button" title="Stop video" onclick="this.style.display='none';document.getElementById('video_container').innerHTML=''; document.getElementById('video_container').style.background='';document.getElementById('video_container').style.color=''; document.getElementById('video_container').style.zIndex=0;"> X </div>
<div id="video_container" ></div>
<div id="hider1">
<iframe style="position:absolute;width:100%;height:100%;" src="http://www.youtube.com/apiplayer" frameborder="0"></iframe>
</div>
<div id="hider2" ></div>
<div style=" CURSOR: pointer" onclick="expandcontent('K6')"><font size="2" color="#800000">MENU</font></div>
<div id="K6" class="switchcontent" style="position:absolute;z-index:100">
<div style='position:fixed; left:50%; top:50%; margin-top:-170px; margin-left:-310px;WIDTH: 100px;height:120px;background-color:#C7CFB4;padding:15px;border:#353B27 1px solid;'>
<a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/Cux1bM35e1c?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Sibelius</a><br >
<a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/LB3VfxfBlnY?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Errol</a><br >
<a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/jUvcyyU7UB4?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Arkansas</a><br >
<a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/jTls82o-ChA?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Chimp</a><br >
<a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/Wz1W_omigwg?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Spooky</a>
<div style="position:relative; CURSOR: pointer; margin-top:10px;text-align:right;"onclick="expandcontent('K6'); "><font face="Tw Cen MT"><font size="2" color="#873800">close</font></font></div>
</div></div>
<div style="position:relative;margin-top:40px;margin-bottom:40px;">
<ul class="semiopaquemenu">
<li><a href="http://ddr4.blogger.ba/">Home</a></li>
<li><a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/Wz1W_omigwg?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Spooky</a></li>
<li><a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/jTls82o-ChA?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Chimp</a></li>
<li><a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/jUvcyyU7UB4?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Arkansas</a></li>
<li><a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/LB3VfxfBlnY?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Errol</a></li>
<li><a href="javascript: void(0)" onclick="include_video('http://www.youtube.com/v/Cux1bM35e1c?version=3&rel=0&autoplay=1&showinfo=0&start=0&autohide=0')">Sibelius</a></li>
</ul>
<div class="bottombar"></div>
</div></div>
<div id="footer">
<p>2012</p>
</div>
</div>
</body>
</html>
Arie