I want to design a page that displays my name. When the site starts working, the page takes the entire width and length, but when 15 seconds pass, I want it to be placed in another place to be replaced by another page, and so on
Here's a solution from what I understand of your question:
document.onreadystatechange = function () {
document.getElementById('content').style.display="none";
var state = document.readyState
if (state == 'complete') {
setTimeout(function(){
document.getElementById('load').classList.remove("center");
document.getElementById('content').style.display="block";
},1500);
}
} .center{
width:100%;
height:100vh;
display:flex;
justify-content:center;
align-items:center;
z-index:9999;
}<div id="load" class="center">Your name</div>
<div id="content">Content</div>