Change main post width

Hi and Good Evening
Before I posted this topic, I tried searching the forum, and used some of the suggestions that were used to similar wordpress but none of them work. I have been looking at this code for 4 hours. there is only 2 problems I am running into.
The link to the site is http://rebeccasrubberroom.com/news.html

1st one is:
The wp is homed in an iframe. the width is 800px but some there is a gap between the border and the page. like there is a margin of 20 or more px when there is none. In addition I hid the vertical scrolling. The page itself, the width is 800px.

2nd
In IE the post looks fine but when I go to firefox the image is overlapping the previous post. i even tried putting <p> codes and it doesn’t make a difference.

any help will be okay, i’ve been through about 20 or more topics trying to find this solution.