From http://www.mtgsy.net/kb/DNS/Advanced_http_redirects_using_the_dns_editing_page
Whilst the management panel can provide 'simple' web forwarding, there are sometimes cases where more advanced web forwarding is required. Examples are forwarding a naked domain (just the domain name part without the 'www.') to your www.yourdomain.com for example. This, simple as it sounds often causes issues.
Advanced forwards automatically take care of the issues forwarding sub domains, naked domains, etc.
To create a redirect record, simply add a new dns record using the 'REDIRECT://' record type. This is a special type of record that configure our web servers to forward your requests to another web site. In the data column put the full url you want to forward to, for example, http://www.mydomain.com. To forward the naked domain, leave the 'name' column empty. To forward a sub domain, put the name of the sub domain in the 'name' column, for example 'support'.
There are different types of redirects such as 301, 302, hidden frame, etc. In most cases, leave it as zero.
301 redirect type, moved permanently. We suggest you do not use this without good reason as a 'permanent' redirect is just that. It will be cached by search engines and users browsers directly and you may have no way to disable the forward at a later date as this data is stored locally on end users machines, not on our systems.
Stealth forwarding - keeps your url in the browser url bar rather than showing the real url
Explicit forwarding is the default and will make www.yourdomain.com go to www.myotherodmain.com. It will also make www.youdomain.com/subdirectory go to www.myotherdomain.com. If you require that www.yourdomain.com/subdirectory go to www.myotherdomain.com/subdirectory, then do not use explicit forwarding.