How to get rid of background colors in slices

Hello Everyone. I was wondering how to get rid of the background in a slice. For example: I was saving a link so I had a work in a slice. However, I made the slice big to match the size of the rollover version of the slice. However, I only need the words from the original slice; not the background color. So basically I want to know how do i make the background color of a slice and everything around it clear. Thank you in advance and I hope my explanation wasnt too confusing. Adios!

Michael,

If I follow you, you need to optimize that slice as a GIF so that transparency will be retained.