While trying to delete Master Page or PageLayout, showing an error 'Server Error : This item cannnot be deleted because it is still reference by other pages
Here is the solution
1) Open the application in Sharepoint Designer
2) Expand Catalogue-> Master Page section where master page and page layout listed.
3) Create a folder say 'Need to Delete' by right clicking masterpage(Masterpage Gallery)-> New-> Folder
4) Cut the Master Pages or Page Layouts need to delete and paste it into 'Need to Delete' folder
5) Delete 'Need to Delete' folder
6) We can delete the required files without showing any error