This is a simple text file with a .txt extension. 

I made this file in the SiteSpinner text editor, 
pressing Enter after each line. Word wrap does not
work for browsers displaying text files, so therefore 
you need to enter hard-coded carriage returns. There
are probably text editors that will make hard
returns automatically -- I have not looked for one.

I then saved the file in my publish folder with a .txt
extension.  The page I specify in the Iframe link
is simply IframeTextSample.txt -- this assumes that
when I publish, the txt file will live in the same
folder as my html files.

In text files you obviously can have only text, no
links or images.  

But the format is very compact, fast loading and
easy to create.