Performance Calendar » The new Twitter

Performance Calendar » The new Twitter

URL Routing
Many people have noticed that the new Twitter.com brought a small change to the site’s URL structure: the introduction of a /#!/ at the front of the path. This is a simple change that most front-end engineers are already familiar with, but with huge performance savings. We can track changes in the application state using the URL, but without a new page load. We also get history and back button support in modern browsers, and can update state as the user edits the URL due to HTML5′s new hashchange event. The #! is there to comply with Google’s Ajax crawling specification, so we don’t lose out on search engine rankings with the new scheme.

Getting Started - Making AJAX Applications Crawlable - Google Code