The localStorage object in modern browsers is a super useful tool for persisting local data, but debugging it is a pain, and it's hard to know what's being stored on your machine. I made a small bookmarklet that lets you inspect and clear data from a domain's localStorage.
Try it out on this page by clicking this link- localStorage inspector. There is some sample data you can inspect on this page. If you like it, simply bookmark that link, and use it on any page.
If you're looking for source- check over here.
Hope it helps!