Add Your Own HTML
  Type or paste HTML in the text box below.
  Enter or paste HTML in the text box. You will see the results of your HTML code on the page where you inserted it after you click Done.

If you are unsure about the quality of the code you are about to insert, create a new page and try it there. That way if the code is incorrectly formatted and results in the page being uneditable, you can just delete the entire page.
Done

Warning: Incorrectly formatted HTML or JavaScript could corrupt your page.