I have read up on this and I'm not getting any of the same errors others have solved. I created a new page, titled it "Store", pasted the code from amazon for an inline frame:
<iframe src="http://astore.amazon.com/myusernamegoeshere-20" width="90%" height="4000" frameborder="0" scrolling="no"></iframe>
Made sure I was in text format not visual, clicked update rather than switching to visual (though I tried it both ways), and the code disappeared. I went on numerous helpful threads where people were having trouble with error messages and whatnot, but I didn't get any error messages.
If I paste the code then switch to visual, a weird orangey translucent box shows up, but even that disappears when I click update. If I change the sizes of my inline frame, I can change the sizes of what orangey box I get, but I can't make it not disappear.
Even when I copied sample code from help threads and pasted that in instead of the code straight from amazon, no luck. It all just disappears. I used by dropdown menu to try setting the format of the page to no borders, but it made zero difference.
I'm using the theme "Ever After". Could it be my theme? Do I need a plugin? It's tough to figure out what the problem is when absolutely no part of it is working. Help!