Dreamweaver and Other Web Page Stuff
The Adobe Dreamweaver web page may be helpful to you. But since Dreamweaver was sold to Adobe, it doesn't seem quite as easy to find what you need. I finally found where to search for downloadable extensions: Adobe Exchange. They also have a Support page for help. Good Luck!
After downloading an extension from the Adobe Exchange page, start Dreamweaver and open the "Commands" drop-down menu. Click on "Manage Extensions...", then "File", then "Install Extensions...". Find the extension file at the location that it was saved to. Select it and choose "Install". Extension Manager installs the extension. Instant Superscripts & Subscripts is found for use in the "Insert" drop-down menu under "HTML" and "Special Characters".
Another site which might interest you is the Animation Factory. They have free GIF animations and graphics (thousands of them if you want to pay to become a "member.")