When you are developing web applications is essential inserting HTML code in your website. There are many ways to do it: with iframe, with embed, and so on. But W3C recommends using the object tag:
Source code of the demostration
To try the demo, copy this code and paste it into a text editor. Then save it as example.html and, finally, open the file with a browser.
<title>Embed HTML in a web page</title>
<meta charset="utf-8" />
<object type="text/html" data="http://dl.dropbox.com/u/11968143/apps/calculator/index.html" width="330" height="440"></object>