Some new features in HTML5 are really useful, like Web Storage, but you have to make sure you understand how it works and make sure you use it in the correct scenarios. There are actually two ways that HTML 5 Web Storage works: local and session storage. I ended causing some end-user confusion by using local storage all the time, so here is breakdown of how both work and when they should be used.
When using window.localStorage, the data associated to this object will never expire. So long as you don't uninstall your browser (or forcefully delete the data), the data held within this object will remain forever.
When using window.sessionStorage, this data will only be retained for a browser session. Meaning that once the user closes the browser instance, the data is gone.
This is useful when you have a search page and want to always retain and show the last criteria entered by the user. But once the user closes the browser, you want the data to be gone, so when he or she re-enters your application the next time, they start with a fresh page.