title: Detect if a web site is already open and reuse window
body: <p>I'm trying to find out if there is a way to open a url link in an email and reuse a window if a certain page ( or site ) is already open.
  What I have is a 'forgot password' page where the user enters their email address and gets asked a security question, this then sends a plain text email with a url link (so no html link attributes) and reports to the user that it has done a good job . When the user clicks on the link it opens up a shiney new browser window and ignores the old report page leaving it feeling sad and unwanted. I would like to know if there is a way to reuse this window or more specifically the forgot password report page. Perhaps I could name the page with javascript or detect if the url is already open somehow. 
  Or is it possible if I did decide to use an html email, so most people would get the benefit.</p>
  
  <p>Please help my report page to loved and wanted again.
  Thanks</p>
  
  <p>I am using PHP and I could use javascript or jquery browserside, or anything else that might fit in with this</p>