If you've ever used JSFiddle, Codepen, or others, this problem will be familiar to you: The goal is to take some HTML, CSS, and JS (stored as strings) and create an iframe with the code loaded inside. You can view it in action here. The content of an iframe element can be just text, or it can contain text-level (inline) markup, or even block-level markup (such as the p markup for a paragraph above). Valid, but maybe don’t use. allow-scripts lets the loaded iframe run scripts (but not create popups). Optimize & style as needed. top: 0 and left: 0 are used to position the iframe at the center of the container. If the content inside is bigger, scrollbars have to suffice. Some screen readers indicate that iframes are present and may even support navigating them along with standard frames. If they are equal, then the page is not in an iframe; otherwise, a page is in an iframe. Note − The frameborder, marginwidth, longdesc, scrolling, marginheight attributes deprecated in HTML5. Most of the attributes of the