title: 500 internal server error when using reverse-proxy
body: <p>I have apache2 installed on my <code>Ubuntu 14.04 server</code>. In port 80 apache running while in <code>port 9000 nodeJs</code> app is running with forever. So I added to following lines to port 80 virtualhost 
  in the apache2 config file to run nodeapp in port 80 using reverse-proxy. But now when I visit my site with port 80 I get and <code>error of 500</code></p>
  
  <pre><code>    ProxyPreserveHost On
      ProxyRequests off
      ProxyPass / http://128.199.136.209:9000/
      ProxyPassReverse / http://128.199.136.209:9000/
  </code></pre>
  
  <p>The app runs well <code>in port 9000</code>. What is the error got this ?</p>