title: how to add something like onhashchange, but for href
body: <p>the <code>onhashchange</code> is great for when the link is "#somewhere", but would like something for <code>location.href</code> instead of merely <code>location.hash</code></p>
  
  <p>if I can handle the request through Ajax, then will reload part of the page.  otherwise will follow link.</p>
  
  <p>would like url in location at top of page to reflect the clicked link.</p>
  
  <p>is this possible?</p>
  
  <p>if site is www.example.com/sub1/page1</p>
  
  <p>if user clicks on www.example.com/sub1/page2, I can handle this in Ajax.  I will redraw part of the page.  I wish the location bar at the top of the page to say www.example.com/sub1/page2</p>
  
  <p>if the user clicks on www.example.com/sub1/page3, I cannot handle it in Ajax.  I wish to href to behave as normal.</p>
  
  <p>so I need to grab changes to <code>location.href</code> and allow or disallow browser to behave in default manner</p>