Product list page not displaying correctly

Not sure if this is an installation problem or not but I've successfully upgraded from 1.8 to 1.9. However, on the product list page, the centre column isn't displaying correctly as it's too wide - causing it to encroach and overlap onto the right side column. What do I need to modify to correct it? (e.g. http://h1workwear.com/category/56-t-shirts.aspx)

Thanks

Hi, its a style issue.

you are using ThreeColumn.master  page

but I think you have edited the wrapper for the central column and made it too wide