For future tracking codes, the following procedures are correct. 

For one dynamic code that reads the process which is the usual process:

Developer --> Insert in HTML <HEAD> 


For other implementation: 

Confirmation / Booking finalization  - Developer  --> Confirmation Page Insert in HTML <HEAD>

Search code - Booking Page --> Page Design --> Content --> Property Description 1

Shopping cart code - Booking Page --> Page Design --> Content --> Guest Details Header