Video does not open in DIV

Question

I am replacing my IFRAMES by DIVS, but I noticed that a scroll bar is not displayed when the page is extensive and also not displayed the video players of my page within the main DIV called content, because ?

Follow my code:

Javascript

<script type="text/javascript">  
try{  
xmlhttp = new XMLHttpRequest();  
}  
catch(ee){  
try{  
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");  
}  
catch(e){  
try{  
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");  
}  
catch(E){  
xmlhttp = false;  
}  
}  
}  
div_base = "";  
function abre(arquivo,metodo,div){  
div_base = div;  
xmlhttp.open(metodo,arquivo);  
xmlhttp.onreadystatechange=conteudo  
xmlhttp.send(null)  
}  
function conteudo() {  
nova_div = div_base;  
document.getElementById(nova_div).innerHTML="<div style='top:50%;left:50%;
position:absolute; overflow:auto;'>carregando...</div>"  
if (xmlhttp.readyState==4){  
document.getElementById(nova_div).innerHTML=xmlhttp.responseText  
}  
}  
</script>

html

<a href="javascript: abre('minha_pagina.html','GET','conteudo');">
Minha   Pagina</a>

<div id="conteudo"></div>

Thank you