If you have chosen Advanced Archive Publishing, this setting dictates the root URL for your archives.

Example: http://archives.example.com/

The rest of the URL for each archive file is created in the format specified in the Archive Map file path for each particular type of archive in the archive mapping section of the weblog's publishing settings screen.

If your Archive URL is identical to or underneath (in hierarchy) your Site URL, it is recommended that you do not use Advanced Archive publishing, but instead add the extra path information specified in the Archive URL to the beginning of your Archive Map File Path.

For example, if your Site URL is http://www.example.com/ and your Archive URL is http://www.example.com/archives/, you would add archives/ to the beginning of each of your archive file paths (using the Custom option in the dropdown), and disable Advanced Archive Publishing.