To resolve this issue, from the Safari menu, choose Preferences > Privacy. Then, choose an option other than Always for blocking cookies.
Note: The default option for Safari is to block cookies "From third parties and advertisers" and is recommended for most usage.
If you want to block cookies temporarily when visiting websites, choose Safari > Private Browsing. Learn more about Private Browsing.
If you reset Safari, or remove cookies that iTunes uses from Safari preferences, iTunes may ask for your Apple ID when you open it next.