apex:define Tag Precedence in Visualforce Templates

I learned something interesting through trial-and-error yesterday:

If you define a set of templates where each successive template "extends" the previous template, the apex:insert tag in all previous templates are available for definition in the final implementing page.

For example, let's take take the following hierarchy of templates:

1. SiteMasterTemplate
2. SiteDepartmentTemplate--contains an apex:composition with template="SiteMasterTemplate"
3. SiteProductTemplate--contains an apex:composition with template="SiteDepartmentTemplate"

Now, if we create a page called SiteSuperMotor that contains an apex:composition with template="SiteProductTemplate", our page can actually use apex:define that define apex:insert elements in SiteMasterTemplate!

Furthermore, let's say that we have apex:insert elements in both SiteDepartmentTemplate or SiteProductTemplate that share the same name attribute as an apex:insert in SiteMasterTemplate, then the SiteSuperMotor page's apex:define would only define the apex:insert in SiteMasterTemplate!