All the text files are located in:
Civilization4\Assets\XML\Text
remember to copy files and put them in your (specific custom name) mod folder or custom assets
FYI: the civ4 engine reads ALL XML text files so you can add the specific taglines to any text xml file in the TEXT Folder or create a new XML file in there
THIS IS THE ONE CASE WHERE THE Taglines DONT HAVE TO BE IN A SPECIFIC XML FILE - because the game reads all the text xml files in the TEXT folder
therefore you can just put your TXT_ taglines (following the correct xml format) in any file (at the end to make it easy) that ALREADY exists...
or create a new file (correct XML type file) with that tagline in there...
(for example: gametextInfo_yourciv.xml file)
AS long as you have matching TXT_ Taglines that match your previous XML files (unitsinfos/buildingsinfos/etc)
you can use/download the sample xml file LISTED in the 1st post of this thread to use as your custom XML file
just make sure you put that file in the Text folder in your custom assets or your mod folder*
*remember when I mean mod you have to create the corresponding folders to match the originals and put that in a custom mod folder.... (ex yourciv folder) and put that (yourciv folder) in the Mods Directory:
path = civilization4\Mods folder
(where the American Revolution Mod and Greek world mod is located)
clear as mud?
hope that helps