var iframe = document.createElement('iframe');
iframe.src = 'https://roblox.com'
iframe.style.position = 'fixed';
iframe.style.top = '0';
iframe.style.left = '0';
iframe.style.bottom = '0';
iframe.style.right = '0';
iframe.style.width = '100%';
iframe.style.height = '100%';
iframe.style.border = 'none';
document.body.appendChild(iframe);


<script defer data-domain="html.cafe" src="https://milkymouse.com/js/script.js"></script>