You should be able to do it by putting this in your html:
Code:
<meta http-equiv="Refresh" content="X; URL=www.mydomain.net/forum" />
(obviously you'd change the X to the number of seconds you want, and also change the url).
You can also do it in javascript. If you look at the bottom part of the STANDARD_REDIRECT template there's code that does it in javascript unless the browser has javascript disabled.