Need an option to go back to a previous web design

[900ranae843sebold489]

I'm creating a website for a client in which he wants a link that people can click on to go back to the previous website design and go to that design every time they go back to that website. How would I go about doing this? Would I need to create a cookie and if I do how do I do that?Thanks for all your help, I'll come back to this question when I get to doing this part!