I can use Twitter to show an example of what I'm talking about. If you use Chrome or FF and go to http://www.twitter.com/#!biz you'll get the rewrite of http://twitter.com/#!biz no problem, perfect. But using that same URL (with the 'www') in Safari and IE7/8 will rewrite the URL back to the main Twitter URL, without the 'www' but no hash and fragment, no deeplink. It's the same result for the Twitter URL that has #!/biz ( with the second / )
If Twitter doesn't (or can't) do anything about this Safari/IE & 'www' behavior, then maybe I shouldn't sweat it either? Is this a browser thing because there's no solution using mod_rewrite within a .htaccess file to store a hashtag fragment, right?
Specifically in my work, I'm using SWFAddress, which uses the hashtag to deep link in Flash content, which is almost exactly like a Twitter URL, except there's no '!'. I think Twitter is using the Making AJAX Crawlable approach. And just like Twitter, my URLs will rewrite fine in FF and Chrome, but bonk in Safari and IE 7/8. It doesn't seem to make a difference if the hashtag has the '!' or not, it's still part of the fragment, no?
I started to play around with a SWFAddress version approach of Making AJAX Crawlable back when I was looking for a solution to make the content on a Flash site crawlable, but the browsers handle the mod_rewrite the same way. The removal of the 'www' works fine in FF/Chrome, bonk the fragment in Safari and IE. I have a working example for my SWFAddress Making AJAX Crawlable approach version (had to remove the link. new users to stackoverflow only get 2 URLs per post). In the end I didn't use that approach for making my Flash content searchable, but it looks promising. I think making the HTML snapshot was more work than using PHP pages, but that's a totally different subject/question.
It'd be funny if (for my first stackoverflow question) there was a really short answer like, Yeah, don't sweat it! :)