At the bottom of the store, there is a yellow tab that reads To accept cookies from this site, please click the Allow button below. By default, the page retrieved from the cache always includes the yellow bar, whether or not the user has clicked Allow.
This behavior should vary from user to user, and there are two ways to accomplish this: a javascript-based plugin, and cache vary rewrite rules.
The more efficient option is a javascript-based solution. A javascript plugin would only need to store one copy of the page and would build the display based on the existence of the cookie. If a rewrite rule-based answer is preferred, the site can be configured to vary on the cookie by adding the following rule to your site's .htaccess file:
RewriteRule .* - [E=cache-vary:user_allowed_save_cookie]
When a customer clicks Allow, the cookie user_allowed_save_cookie=%7B%221%22%3A1%7D;
will be created. Using the rewrite rule above, the cache will vary on that cookie. This means the cache will store two copies: one that shows the yellow bar at the bottom, and one that does not.