Dhavidy Luiz Mamede Pires12,438 Points
Why would you cut from <html> to <div id="content">?
Is it just for the purpose of this introduction on php or any reason in specific? Because you'd loose the ability for optimization on each page as they have the same <head> tag.
The reason that you copy this whole code is that it is in deed the same on every page. You're right about the fact that you can't make specific changes for every single page. Later in the course you'll learn to manipulate content in the header for a specif page/situation, using php. Just keep following hte course and you'll find out what I mean. ;)