“The Past, Present, and Future of Local Storage for Web Applications”
local storage is one of the areas where native client applications have held an advantage over web applications.
Cookies are included with every HTTP request, thereby slowing down your web application by needlessly transmitting the same data over and over
Cookies are included with every HTTP request, thereby sending data unencrypted over the internet (unless your entire web application is served over SSL).
Cookies are limited to about 4 KB of data — enough to slow down your application (see above), but not enough to be terribly useful
So what is HTML5 Storage? Simply put, it’s a way for web pages to store named key/value pairs locally, within the client web browser.