Is there any way i can create some sort of constant that i can just use one word in my html document and add my header into it and making one change in the header will change the header for all the pages. This is so i dont have to copy and paste it to every page and make one change and have them apply to the header on all the pages.
You can use Javascript to edit the content and link the JS File in all of your HTML Documents.
You can also use CSS with content property and also link CSS File in all of your HTML Documents.