title: Address web path in config.yml in Symfony2
body: <p>When configuring one bundle in Symfony2, I needed to set up a static path to CSS file from <code>web</code> folder, i.e. a line from <em>config.yml</em>:</p>
  
  <pre><code>content_css: "%path_to_web%/bundles/mybundle/css/styles.css"
  </code></pre>
  
  <p><code>%kernel.root_dir%</code> returns the absolute root server path, but what in this case is the way of getting a <strong>virtual</strong> path to <code>web</code> folder? Is there any special variable for that or do I need to hard code that path?</p>