Raindrops theme: How do I edit caption and iframe formatting?

I have a couple of tweaks I need help with:

1. I’d like to change the caption formatting to remove the color background so it matches the rest of the page – in other words, no border or color at all around the pic, and the text underneath on the same color ground as the page. I also want to format the text in italic.

2. I’d like to remove the white keyline from the Amazon ad. I chose Do not show border on Amazon’s html adbuilder page but I couldn’t see any difference between that and the code for Show border, so maybe I need to edit it.

My site: http://vendettamask.net/buy-v-for-vendetta-mask-at-amazon-co-uk.html

Thank you for your time, trouble and expertise.