How can I edit all of the templates, messages, and default index.html pages?

If you're looking to customize the look and feel to the data that is used for your users, this guide will explain where these files are, and how to go about editing them. (note that this doesn't apply to skins)

To edit the default index.html placeholder file that new domains will get after being created, you will edit the index.html found in /home/reseller/domains/default/index.html, where reseller is the name of the account that will create the User. If a User creates a secondary domain in his account, this same path still applies (that of the User's creator)

One level above that, when a new Reseller or Admin is being created, this "default" directory is created and filled with defaults. After their account is created, they will use these files as mentioned above. If you want to edit the default files that are copied into /home/reseller/domains/default, you can find these defaults in: /usr/local/directadmin/data/templates/default
However, you must ensure to follow the "templates" editing guidlines, which will be discussed next.

Message and templates can be found in:
/usr/local/directadmin/data/templates
Files here are read in, usually "tokenized" (variable swapped with real values) and used for their respective purposes. Templates can be editied to customize the look and feel of this data, however there are few rules that need to be followed to ensure your data stays intact.

The templates directory comes in the DirectAdmin update.tar.gz package, so after each update of DirectAdmin, all files in the templates folder are overwritten. This allows the templates to stay updated to their latest version.

If you wish to make changes to these files, in order to prevent updates from overwriting your changes, you simply first copy the template file that you wish to edit to the custom folder: /usr/local/directadmin/data/templates/custom

then edit the copied file that's in the custom folder. Files in the custom folder override the files in the templates folder.

For the first example of directory templates (like the default/index.html) if you want to customize the index.html for new Resellers, then you must copy the whole directory (and it's full contents) into the custom folder, eg:
/usr/local/directadmin/data/templates/custom/default/*

Note that the placeholder index.html for the domains owned by a Reseller is taken from his creator, not his own default directory. So if "admin" where to create Reseller "bob", then bob's own personal domains will grab the placeholder index.html from /home/admin/domains/default/index.html, and not his own default or the templates default.