title: Difference between <% ... %> and <%= .. %> in rails 3
body: <p>I have test method in helpers/application_helper.rb file:</p>
  
  <pre><code>def test
    concat("Hello world")
  end
  </code></pre>
  
  <p>Then, in index.html.erb I call as:</p>
  
  <pre><code>Blah
  &lt;% test %&gt;
  </code></pre>
  
  <p>The browser display:</p>
  
  <blockquote>
    <p>Blah
    Hello world</p>
  </blockquote>
  
  <p>It's normally, but if I change </p>
  
  <pre><code>&lt;%= test %&gt;
  </code></pre>
  
  <p>the browser display:</p>
  
  <blockquote>
    <p>Blah Hello worldBlah Hello world</p>
  </blockquote>
  
  <p>It duplicate all of page. I don't know why?
  What difference between them?
  Thanks for your help!</p>