To remove an old form from a page, find the area of the page that is bounded
by a gray box with dotted lines. It probably looks something like this:

Delete all the contents inside the dotted line box. Once the contents are deleted, the dotted line box should disappear. If the dotted line does not disappear, try putting the mouse cursor right before the box and press the Delete key until the box disappears.
You will need to find <FORM> and </FORM> tags. Generally if you delete everything between these two tags and the tags themselves, you will delete the form. Consult your HTML editor's online help for further instruction.