title: What is the meaning of null in Mage log (magento)?
body: <p>In order to create Magento log, one would write something like</p>
  
  <pre><code> Mage::log('Server Side Validation kicked in for Year for '.$currentYearType);
  </code></pre>
  
  <p>But if I were to add the log in a sepearate file , do I  </p>
  
  <pre><code>Mage::log('Server Side Validation kicked in for Year for ' ,null,'serversidevalidation.log');
  </code></pre>
  
  <p>Please correct me if I am wrong.</p>
  
  <p>If so, what is the use of null in the middle?
  Also, does the file need to exist before hand or I think it is created by system when needed. Am I right? Also, will it include timestamp?</p>