It seems to render correctly in Firefox but not IE so it might have something to do with IE's different interpretation of CSS margin and padding.
You might try reducing the width of your #newsdetailrightbg CSS id from 721px to 700 to see if that has any effect.
BTW, using the Firebug addon within Firefox is a great tool for CSS troubleshooting/tinkering. I wish there were something similar for IE.
TM