When you edit a site content type through the user interface and make a change on a content type settings page, all the settings contained on that page are overwritten during the push-down operation.Therefore, the granularity of the changes that you can push down is defined by which settings are grouped on each page.Also, we might see duplicate columns in the content type in the library settings.
For example, suppose that you make changes to a column in a child content type.
If you then make other changes to that column in the parent template or even delete that column, and you push down the changes, Share Point Foundation overwrites the changes that you (or more likely, someone else) originally made in the child content type.
Share Point Foundation does not add the column back into the child content type.
If you try to perform a push-down operation on a child content type that is marked as read-only, the push-down operation fails unless you set the parent content type to be read/write as part of the push-down operation.
, changes that are made to a parent content type to its child site and list content types.