On Page 98, the proposed changes to app.html.eex include the following code:

    <a href="http://phoenixframework.org/" class="phx-logo">
        <img src="<%= Routes.static_url(@conn, "/images/phoenix.png") %>" alt="Phoenix Framework Logo"/>
    </a>

However, the compiler is complaining about the syntax and suggests the following:

    <a href="http://phoenixframework.org/" class="phx-logo">
      <img src={ Routes.static_url(@conn, "/images/phoenix.png") }
          alt="Phoenix Framework Logo"/>
    </a>

So basically the <%= element is not allowed within attribute values and braces should be used instead.

I guess this might be a change in how Phoenix Templates work added after the book was published?