how can i create subcategories for my website?

Hello, I built my own website and i would like to have pop up subcategories. We sell gift baskets so the subcategories would be by occasion such as birthday, get well, sympathy, etc. I would like to have those subcategories so my customers can go straight to their choice. How can i do it? Thanks. www.delightexpressions.com
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Check out this tutorial. http://javascript.about.com/library/blme…
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