Jay-bo you have not taken any notice of pgo WTF comment, although you might think that is rude and sarcastic, that was my thoughts too when looking at that CSS you provided. You have height as a negative value which is illegal for the height property.
certainly providing a link to your site will help as we can all look at the complete css and html and spot any errors. You can check for errors yourself by running the CSS and HTML through validator as most of time pages not doing what they should are a result of errors in code, such as having height set as -500px.
The W3C CSS Validation Service
The W3C Markup Validation Service