iFrames are a way of inserting one HTML document into a defined area of another HTML document.
1. Create a new HTML document
2. Copy this code:
<iframe src ="html_intro.asp" width="100%" height="200px">
<p>Your browser does not support iframes.</p>
</iframe>
3. Paste it into the code view of your document. Modify the document that is being called to open any other document in your root folder, or use an absolute URL like http://www.webmonkey.com
Example:
More on this here: http://www.w3schools.com/TAGS/tag_iframe.asp