Alert after completion of download.

Please help me out in this problem.

I have a jsp which is having a link to static zip file on the server for download. If user clicks to that link download window(default one) will pop up and ask the user to save the file.
I need a javascript method which should give alert message after the file has been downloaded successfuly. (If somehow file has not been downloaded properly then no alert should come.)

JavaScript has no control over the download. It does not know if it was downloaded or not so you are out of luck.

Eric