The only way to prevent people downloading things from your website is not to put them on your site in the first place. Here's how a website works:
Computer: Hey, Example.com Server, can you send me the page "cupcakerecipes.html"?
Example.com Server: Why, sure I can. Here's the page.
Computer: I see this page includes the image "deliciouscupcake.jpg" — can you send me that image so I can show my user the delicious cupcake?
Example.com Server: Oh, yeah, here ya go, buddy.
Computer: Hey, sorry to bug you again, but I see the page wants me to run the script "animatesprinkles.js" — can you send that too so I can run it?
Example.com Server: Of course!
See, at each step of the way, the user's computer is downloading the resources he needs. If you do not allow the user's computer to download your images and scripts, he can't see them or run them.