What allows browser Back button to work w/o repost?

[Guest]

hi group! we've created a search feature that relies on custom tables in our database. we've obviously overlooked whatever allows the user to use their browser Back button without a refresh/repost.

 

you can see this in action at http://think4inc.com when you use the Ink And Toner Search in the top of the left hand column. once you select your manufacturer, you can't go back without repost. it stays this way right into checkout.

 

can someone point us in the direction of the function that handles this?

 

thanks!