Bing Webmaster blogs to help web publishers and Content Management Systems (CMS) companies providing Search Engine Optimization (SEO) best practices for AJAX URLs.
With pushState, you can generate almost any URL you want in the browser's address bar. Search Engines will crawl and index the same URL used by your customers such this URLs schema http://domain/path/file?name=value_parameters.
"We are still supporting the #! crawlable AJAX method but as I said, we do not recommend it at all and we really prefer pushState which is far easier for webmasters and web developers to adopt and maintain," said Bing's Fabrice Canel.
Here are a few things to keep in mind:
Avoid broken links. As a best practice avoid broken links creating URLs with pushState is to limit change to URLs query parameter values. "Search engines discovering this link should be able to see the same content as well (and remember that Bing recommends you avoid cloaking)."
Avoid duplicate content. With pushState, a web site may start to generate way too many URLs. Bing advises to use pushState to inject all useful parameters before the question mark and all -- at least from a search engine's perspective -- "useless" parameters after the fragment part of the URL (that is, after the #).
For instance, for a music player web app that offer the ability to pause a song and bookmark it, use the URL http://www.example.com/musicPlayer.aspx?song=TheCanadaSong#pausedAt=42 (instead of http://www.example.com/musicPlayer.aspx?song=TheCanadaSong&pausedAt=42).
As, the latter URL may lead to many duplicate content URLs. The Ignore URL Parameters tool in Bing Webmaster Tools can help mitigate this issue, but it is better to avoid it beore.
Bing advises that for browsers and crawlers that do not yet support pushState, "you should continue to offer links that allow direct navigation to a URL for a given page state."
While, for customers with pushState support, "you can refresh parts of the web page and update the URL," Bing said.
Update 03/26: Google has long been supportive of HTML5--now it has published a video in support of HTML5 pushState.
"A correctly implemented site that uses pushState typically doesn't need any extra support in order for us to be able to crawl it. We do support both [pushState and #!] and we do handle both standards… but [pushState] is something that I would encourage you to look into and it can be quite helpful in making sure things can be crawlable," noted Cutts in the video.