So I just got my new domain, And I don't wanna constantly edit 40+ Lol. So I was wondering, is there any code and way to add it.

Please be detailed, I've spent HOURS Trying it once, and f*cked up.

you could put the header in your style.css code or whatever you called your style code. Then your footer can go in a seperate code. I have my nav included with a php include tag so I would put it in there but I don't know if your doing that or not.

I use smart ftp client.

Like...My friend tried and it's confusing, like every time I do what they say I mess up.

You need to use a php include code and change all of your pages to have a .php ending.

<?php include ("/pagenamehere.css"); ?>

That would be the basic code and the other one is for if you have pages in different directories (folders) and don't want to have to copy the .css page over and over again and add it to every directory then edit all of thos also.

<?php include($_SERVER['DOCUMENT_ROOT'] . '/pagenamehere.css'); ?>

The only thing that you would change in both of those would be the pagenamehere.css to your CSS or HTML page.

you could use an iframe

You can use php to solve your problem.

You can create two file header.html and footer.html that will be used in all your files. In your main file that you will be displaying to the public you can use the php include function.