Does this page use valid HTML?

This website is very simple, but it contains invalid HTML. It might look ok in your browser, but it might choke on a browser that is less tolerant of coding mistakes. Can you find the invalid HTML on this page? Try this:

1. Look at the HTML source. See if you can identify the invalid HTML before running it through the W3C Validator. Hint: There are two examples of invalid HTML on this page.
2. Run this page through the HTML Validator. Did you find the same mistakes that the Validator found?
3. Correct the mistakes found by the Validator, save the file, and run it through the Validator again.
4. Repeat steps 2 and 3 until the page validates.