skin/%your_skin%/ - contains skin specific files / templates.
skin/common_files/ - contains files and templates used in all skins until they appear in the
%your_skin% skin directory.
In other words to customize some common template you should copy it to the
skin/%your_skin%/ directory preserving sub-folders structure.
To customize the home page of
2-columns skin copy ->
skin/common_files/customer/home.tpl to ->
skin/2-columns/customer/home.tpl and make the necessary changes to
skin/2-columns/customer/home.tpl
X-Cart:Storefront Design and Layout
X-Cart:Customizing storefront
X-Cart:Editing Skin Files