Plain Text Editing
At the bottom of the editing screen is a button called "Page Properties". In the Page Properties editor there is a checkbox lableled "Plain Text".
Click this check box to edit the page using a plain text area (no rich text formatting). This is useful for managing content that the editor will not accept, such as highly complex HTML, Javascript, and IFRAMEs. You can then include the plain text page into a normally editing page using an include tag.