Buttons overlapping

I used the complex button tutorial to create some buttons that expand a box on rollover. I am using this to create captions for certain points on an image. The problem I am having is the buttons are overlapping. When the box expands it is underneath some of my other buttons. How do you get all the buttons on the same level to prevent this? I have attached my file. Also, here is a link to another website that shows what I am trying to achieve. Click on “Series Highlights” to see what I am talking about. http://www.deere.com/en_US/ProductCatalog/GC/series/GC_gator_t_series.html Thanks for any help!