Have userstyle: (profile\chrome\userContent.css)

@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document regexp(".*?/pushstate-target.html"){
	body:after{ content: 'userstyle works' }
}

Verify by visiting href="./pushstate-target.html"

Try button onclick="history.pushState({},'','./pushstate-target.html')

You should see 'userstyle works' below after clicking above button. (Does not work in Firefox, Nightly, 2012-10-05)