Another option, building upon the column by merlyn linked to by atcroft, would be to employ the Javascript XMLHttpRequest object to communicate with the server and update an element of your web page with the progress (as reported by the server) of a detached, long-running process. The advantage which this method would have (to my mind) is that you could browse away from the page and return at a later stage to check on progress (or have the process checked upon by non-initiators of the long-running process).