Q: Javascript Url manipulation and back navigation I am updating the url with something like this:
window.history.pushState(null, "Page title", "/?param=" + myParamValue);

This works fine, but when the user hits the back button, the url gets updated but the page does not reload.
I have an ajax routine that updates the content but if possible I don't want to mess with re-implementing back/forward navigation, and I just want the page to reload in case of the user hitting back/forward browser buttons.
Q: Is there a way to force the page to reload the given url on browser back/forward actions from the user?
Bonus Q: also, what if the browser doesn't support window.history.pushState on older browsers? Shall I surround that code in a try/catch block?

A: if(typeof window.history.pushState === 'function')
    //handle your url rewriting
else
    //support for older browsers

As for your question about back-button support, the link provided in the comment provides very nice implementations for the feature

A: You should take a look at this jQuery plugin, it might be useful for you:
http://www.asual.com/jquery/address/
I found it reading this thread:
https://stackoverflow.com/questions/116446/what-is-the-best-back-button-jquery-plugin
I hope it helps.
About the old browser question, I don't think you have to bother with that because you are using ajax, which requires a modern browser too. The main question is: who will visit your web site? If it's mainly people over 40yo, maybe you should bother... 
Just my opinion ;)
Edit: Be careful with IE9, it's not handled in it. thx to nbrooks for the info
