SuperRefresh is a bookmarklet I wrote. Here is the README:
A bookmarklet that automatically refreshes your page as you are designing it.
1. Navigate to the page that you are developing in your browser - this can be either a local file or a served file.
2. Click on the bookmarklet - your page will be replaced with the
SuperRefresh page, which will contain an iframe pointed back at your page.
3. Edit your page and save. The changes will almost immediately update within the iframe.
Click here to Try it! Bookmark it to save it for use later. Enjoy. Currently, it works for Safari, Chrome, and Firefox.
The source code is posted at GitHub.