[Support Policy] Supported and unsupported scenarios for working with custom site definitions and custom area definitions in SharePoint 2003, 2007 and 2010

https://support.microsoft.com/kb/898631

Unsupported scenarios

When you work with custom site definitions or custom area definitions, the following scenarios are not supported:

• You modify one of the default site definitions or one of the default area definitions that are included in SharePoint.

  We do not support modifying the default set of site definitions or area definitions that are installed when you install SharePoint. Additionally, we do not support modifying the .xml files or the .aspx files in the default site definition or in the default area definition.

• You modify a custom site definition or a custom area definition after you deploy the custom site definition or the custom area definition.

  We do not support modifying a custom site definition or a custom area definition after you create a new site or a new portal area by using that site definition or area definition. Additionally, we do not support modifying the .xml files or the .aspx files in the custom site definition or in the custom area definition after you deploy the custom site definition or the custom area definition.

• You modify the Webtemp.xml file or the Webtempsps.xml file that is located in the following folder:
  Drive:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\60\Template\LCID\XML

  or

  Drive:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\Template\LCID\XML

  or

  Drive:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\Template\LCID\XML

• We do not support modifying files that reside in the _layouts folder. We reserve the right to update these files in software updates or service packs at a later date. This may cause the custom changes to be lost. You must always back up files that you have changed so that you can restore them at a later date.