is possible we need js experience

user.js:

var list = "html code here"
document.getElemetById("userlist").innerHTML = list;

mysite.com/index.html:
<div id="userlist"></div> <script src="/user.js"></script>

file js -userlister
header code:
var list = "

code:
html here

footer code:
"
document.getElementById("userlist").innerHTML = list;

comment