Final answer:
No public website exists for transferring files from NIPR to SIPR due to the classified nature of the networks. Secure and approved government methods must be used, and the specific process is not publicly disclosed for security reasons.
Step-by-step explanation:
The question 'What website can be used to transfer files from NIPR to SIPR?' is related to a secure file transfer between two different levels of classified U.S. government networks: the Non-secure Internet Protocol Router Network (NIPRNet) and the Secret Internet Protocol Router Network (SIPRNet). Due to the sensitivity and classification of such a transfer, there is no public website that can be used to perform this action. Instead, a secure and approved government method must be used, which typically involves approved hardware and software, proper authorization, and strict adherence to protocol. The specific method and tools for transferring files from NIPR to SIPR are not publicly disclosed for security reasons and would be part of a classified process.