If you registered a new domain name when you signed up for your plan (after January 22, 2001), we automatically locked your domain as soon as it became active. If your domain is locked, you can't change your name servers.

What's domain locking?
Domain locking is a free security enhancement, designed to prevent unauthorized transfers of your domain by "locking" your name servers. With domain locking, only you can make changes to your domain, and unauthorized third parties won't be able to transfer your domain without your permission. (It also helps prevent making inadvertent changes to your name servers, which could interefere with your domain services.)

When your domain is locked, the "Change Name Servers" button on your "Advanced DNS" page will be inactive, and an "Unlock Domain" button will become available. To make changes to your domain name servers, sign in to the Domain Control Panel and turn off domain locking by clicking the "Unlock Domain" button. Learn more.

Note: Still having trouble? If you're in the process of transferring your domain away from Yahoo!, you won't be able to change your name servers. Learn more.