Google for jQuery ajax history plugins. There are many.
also look up jQuery haschange plugin: http://benalman.com/projects/jquery-hashchange-plugin/
basically you append / update (possibly increment) a '#result-set=1' to the page's URL. Then using the haschange plugin for eg. you can trigger your own code, move back or forward to how much of the results were shown by pagination etc. When a user clicks the back button and comes back to your page, the on load firing of haschange should work if you've wired up your pagination to work of the '#...' in the URL