Is it possible to redirect all HTTP requests that come in for http://mydomain/mydirectory/* (including subdirectories) to the same directory structure at http://anotherdomain/mydirectory/?
Yes, all new accounts have this capability.
To create the redirect, you can put the following in your .htaccess file:
Redirect /mydirectory http://anotherdomain/mydirectory
It will traverse symlinks as they existed in the public_html directory.
Please note that .htaccess is not available for "Simple Virtual Host" accounts. A list of the features for each account type is available here. If you need to upgrade your account type, please email email@example.com to request an account type upgrade.
How do I set up an html page to automatically redirect a browser to another page?
You can do that with a META Redirect. In your HTML documents between the<HEAD> and </HEAD> tags, put the following code:
<META HTTP-EQUIV="Refresh" CONTENT="0; URL=http://www.yourdomain.com">
Make sure to replace where it says http://www.yourdomain.com with the URL you want to redirect them to.