If you have forgotten or lost your username and/or password, simply go to the Alumni List, find your profile in the alumni list and click the "Edit Profile" link that appears both above and below your profile. On the login page that then appears, click the "Request Password" link next to the login button. You will then be prompted to verify that you do indeed want the password sent. Click the "yes" button and your username and password will be on there way to your mailbox.
If your email address has changed and you no longer can receive email at the address listed in your profile, then you will need to contact the site maintainer and request that your email address be updated.