HTML - How To Free The Element

Hello,

I am Delphi programmer and PHP web development, I have a problem with the AJAX which is: how to free or close the element, in the Delphi when I create an object in runtime it can be free the object and close it like query, anyway how to close or free the result in AJAX language? below is an exmple:

Code:

var Buffer= document.body;
var getDivBox= document.getElementById("div_box");
var EDivBox= document.createElement("div");
if (getDivBox != null)
{
getDivBox.style.visibility = "visible";
}
else
{
EDivBox.setAttribute("id","div_box");
Buffer.appendChild(EDivBox);
}

with the above code, for first loading it will create to element and while you are in the page it will still create my question is how to close the created element in order to make the page fast because in the localhost I checked the CPU performance and I surprised: it was 100%, when I close the page it go back normal.

any help with this topic is highly appreciated

Regards