I’m not sure what step I’m missing. I copied your html script into a NotePad file and saved it as a .html file. When I access the url you provided I see nothing on the web page that might have been in my clipboard. When I try to use my browser to access the saved NotePad html file I also see nothing.
The latter releases of Netscape are based on the same Mozilla codebase as Firefox, so it probably won’t work.
As written, the html doesn’t do anything but dump your clipboard to the browser window. It’s all client side on your PC. However, you could extend it to make an XmlHttpRequest to another machine and send your clipboard data to someones website.