CKEDITOR 4.2 or later will not allow iframe (or other html tags)
Very easy fix.
Edit the config.js file (inside the CKEDITOR directory)
config.allowedContent = true;
before the close bracket tag.
save the change.
Edit the ewcfg11.asp (or slightly different filename depending on your version of ASPMAKER)
set this line to FALSE:
Const EW_REMOVE_XSS = False ‘ True to Remove XSS / False to skip
quit the open web browser (all open instances of that browser).
launch the browser.
retry pasting IFRAME code into SOURCE on CKEDITOR. Should work now.