How do I allow user to enter & SAVE email addresses ?

I'd like to create a simple little program that will allow users to enter 5 different email addresses of their choosing, and then SAVE that list of 5 email addresses.

Then.. when the user clicks on the button/email address, it will email that person with a pre-determined message.

I can't seem to figure out how to allow the user to enter their own data (i.e. email address) and then have the program SAVE it for future use.

Any ideas?

ajax & textfile would be one way, but thats not a secure one. You save the data in webstorage and send it if he is entering the Game/app