You can use localstorage of HTML5.
window.content.localStorage[key]=value; //Saving window.content.localStorage[key]; //Accessing delete window.content.localStorage[key]; //Delete
Where KEY = the name of the variable you want to store, and VALUE is the string value you want to save. This only supports saving Strings, but if you need to save an object you can "stringify" the object with JSON.
So you can do something like:
You'd better have a look at browser cookie.
You can store data persistently on the browser using either cookies or Local Storage.
Your other option is to store the data on the server on behalf of the current user. When the value is changed in the client, you would make an ajax call to the server so the new value can be stored on the server. You can then either retrieve the value from the server with ajax in a future page or the server can place the current value into the page each time it is requested. You would need some method of identifying the current user (often a user login) so the server could retrieve the proper user's data.