inline frame, RSS feed, & disappearing code

I am using the Autumn Concept 101 theme in my website: http://retireforlessincostarica.com

I am having two similar problems. The first is that I have created a page called “Today in Costa Rica.” I used RSS-include to create an inline frame for an online newspaper in Costa Rica that offers a, RSS feed. I have gotten and inserted the HTML in my page, just under the heading. When I save it and click the “visual” tab, I can see the iframe and contents the way I formatted it. But when I click “Preview this Page” all I see is a 404 Error. Then I check the code and most of the time, it has just disappeared.

I am having a similar problem creating and inserting an inline frame to hold an Amazon.com “aStore”. I use the <iframe></iframe> tags and insert the code between them, but I get that same 404 Error and the code disappears.

I’m a novice at all of this, so any help you can give me will be much appreciated!
Thanks,
MightyA