I have done many works on html5 local storage. I have made a web form to submit data using local [login to view URL] Sql is basically sqlite embedded into the browser. I've used sqlite off-and-on for a few years. At first I was turned off by the name (excuse my superficiality) and by the architecture (just a flat file database). But after digging into it, I found that it's a rock solid platform, and great for production use, as long as you keep in mind its limitations. Its limitations aren't so much size (I think you can go at least 1 GB without a problem), but inherent in flat file databases (high levels of concurrency) and missing features (stored procs and other higher-end database features).
Can do it easily