notepad++ is an text editor, images and videos are, normally, binary files .
You don’t want to use npp while editing those files, an hex editor would be
the better choice.

But what has a website to do with??

A website is located on a webserver and the website is normally written
in HTML and/or scripting languages like php, java, python etc…
If you want to have an image or video included you need to upload the files
by using some file transfer protocol like ftp, sftp, samba etc… and then you
need to reference its location within your web document or reference its external
address.

I guess my answer is now as confusing as your question, isn’t it?

Cheers
Claudia