title: How to show error messages in Joomla Plugin?
body: <p>I have a plugin for Joomla 2.5 which shows error messages like this:</p>
  
  <blockquote>
    <p>Article Rating: Invalid Rating: 10</p>
    
    <p>You already rated this Article today!</p>
  </blockquote>
  
  <p>And I'm creating another plugin similar to this one, but don't know how to show these kind of messages.
  I think is messages are taken from: en-GB.com_content.ini</p>
  
  <p>This is the plugin I'm using as reference: <a href="http://pastebin.com/hcpczq5C" rel="nofollow">http://pastebin.com/hcpczq5C</a></p>
  
  <p>Thanks in advance.</p>