Posting banners/affiliate graphics in HTML doesn’t work

I’m using this theme for an amazon affiliate site.

Every time I try to paste an amazon graphic link in the HTML code (I’ve tried via text widget sidebar area as well as in a basic post) and then hit save, my page literally shows nothing new. It’s as if I didn’t post a thing.

Is this just an issue with the theme itself and not allowing this sort of code to be inserted or am I missing something here?

Please respond, I’d like to know if I should just drop this theme for a different one!

Thanks in advance.