I'm trying to make a website during my spare time and I'm wondering if there is an "external sheet" for HTML like they do for CSS?

I don't want to manually type out/copy and paste the coding into every new page I add.

I'm sorry if you don't understand what I'm talking about. D8

To create a web page in Dreamweaver 8, open the application and select "Designer Workspace." In the Document Window, insert a graphic by using the Insert Bar, hit the "Enter" or "Return" key once to type a two or three word caption underneath the graphic. Then hit the "Enter" or "Return" key two times to type three sentences describing the image. Save the web page by going to the Menu Bar and selecting "File" and "Save As" to name your file. To view your web page, go to the Document Toolbar.

When you have exited Macromedia Dreamweaver 8 and decided you want to change your web page, open the application by going to "File" and "Open" from the Menu Bar. Select the file name to open, then add or delete text. To save any changes to your web page go to "File" and"Save."

To create a web page in Dreamweaver 8, open the application and select "Designer Workspace." In the Document Window, insert a graphic by using the Insert Bar, hit the "Enter" or "Return" key once to type a two or three word caption underneath the graphic. Then hit the "Enter" or "Return" key two times to type three sentences describing the image. Save the web page by going to the Menu Bar and selecting "File" and "Save As" to name your file. To view your web page, go to the Document Toolbar.

When you have exited Macromedia Dreamweaver 8 and decided you want to change your web page, open the application by going to "File" and "Open" from the Menu Bar. Select the file name to open, then add or delete text. To save any changes to your web page go to "File" and"Save."

I don't use Dreamweaver. I'm seriously googling up codes and piecing them together. D8

You should use PHP includes :)

http://codyscode.com/index.php?/topic/57-includes/

If you have many pages you should consider using a CMS, similar to WordPress (http://www.wordpress.org).

Try this tutorial: http://www.lissaexplains.com/html6.shtml#SSI

If your webhost supports php, I would suggest php includes. Its what I use for my website.
This tutorial is really helpful : http://sugarysweet.net/tutorials/coding/phpincludes.php
I've never used SSI, so I don't really know how good it is. Hope this helps! :)