please tell me how to disable print-screen option in mozilla firefox to save my web page.
You can't. Simple as that :)
It might actually be easier to disable the internet, than it is to actually prevent someone from taking what they want from it.
Even if you could disable every single method for every single browser, it is easy to run video out and record it.
The only way to protect content from being taken is to not put it on the internet.