Change Browser Address URL without Relaoding the Page

We have an application where the user enters with a certain URL such as http://some_host/home.htm.  With AJAX, we change the DOM of this first page so that it is identical to another page with a URL say http://some_host/login.htm.  

If the user refreshes the browser or bookmarks the page they will be returned to /home.htm instead of /login.htm.

Is there a way we can use JavaScript to change the URLin the address bar from http://some_host/home.htm to http://some_host/login.htm without actually reloading the page in the browser?  

We need a solution (or less-desirabll of course, a combination of solutions) for recent versions of the major browsers (IE, Mozilla-family, Opera, Safari).