title: nginx status code 200 and 304
body: <p>I'm using nginx + passenger. I'm trying to understand the nginx response 200 and 304. What does this both means? Sometimes, it responses back in 304 and others only 200. Reading the <a href="http://yuiblog.com/blog/2007/01/04/performance-research-part-2/" rel="nofollow">YUI blog</a>, it seems browser needs the header "Last-Modified" to verify with the server. I'm wondering why the browser need to verify the last modified date. Here is my nginx configuration:</p>
  
  <pre><code>location / {
      root /var/www/placexpert/public;   # &lt;--- be sure to point to 'public'!
      passenger_enabled on;
      rack_env development;
      passenger_use_global_queue on;
  
      if ($request_filename ~* ^.+\.(jpg|jpeg|gif|png|ico|css|js|swf)$) {
          expires max;
          break;
      }
  }
  </code></pre>
  
  <p>How would I add the header "Last-Modified" to the static files? Which value should I set?</p>