title: 'Mage_Core_Exception' with message 'Invalid block type: in /var/www/magento1/app/Mage.php:595
body: <p>I got this exception in log file when just create a simple hello world module.</p>
  
  <pre><code>exception 'Mage_Core_Exception' with message 'Invalid block type: MyCompanyName_HelloWorld_Block_Helloworld' in /var/www/magento1/app/Mage.php:595
  Stack trace:
  #0 /var/www/magento1/app/code/core/Mage/Core/Model/Layout.php(495): Mage::throwException('Invalid block t...')
  #1 /var/www/magento1/app/code/core/Mage/Core/Model/Layout.php(437): Mage_Core_Model_Layout-&gt;_getBlockInstance('helloworld/hell...', Array)
  #2 /var/www/magento1/app/code/core/Mage/Core/Model/Layout.php(472): Mage_Core_Model_Layout-&gt;createBlock('helloworld/hell...', 'helloworld.hell...')
  #3 /var/www/magento1/app/code/core/Mage/Core/Model/Layout.php(239): Mage_Core_Model_Layout-&gt;addBlock('helloworld/hell...', 'helloworld.hell...')
  #4 /var/www/magento1/app/code/core/Mage/Core/Model/Layout.php(205): Mage_Core_Model_Layout-&gt;_generateBlock(Object(Mage_Core_Model_Layout_Element), Object(Mage_Core_Model_Layout_Element))
  #5 /var/www/magento1/app/code/core/Mage/Core/Model/Layout.php(210): Mage_Core_Model_Layout-&gt;generateBlocks(Object(Mage_Core_Model_Layout_Element))
  #6 /var/www/magento1/app/code/core/Mage/Core/Controller/Varien/Action.php(344): Mage_Core_Model_Layout-&gt;generateBlocks()
  #7 /var/www/magento1/app/code/core/Mage/Core/Controller/Varien/Action.php(269): Mage_Core_Controller_Varien_Action-&gt;generateLayoutBlocks()
  #8 /var/www/magento1/app/code/local/MyCompanyName/HelloWorld/controllers/IndexController.php(5): Mage_Core_Controller_Varien_Action-&gt;loadLayout()
  #9 /var/www/magento1/app/code/core/Mage/Core/Controller/Varien/Action.php(418): MyCompanyName_HelloWorld_IndexController-&gt;indexAction()
  #10 /var/www/magento1/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action-&gt;dispatch('index')
  #11 /var/www/magento1/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
  #12 /var/www/magento1/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front-&gt;dispatch()
  #13 /var/www/magento1/app/Mage.php(684): Mage_Core_Model_App-&gt;run(Array)
  #14 /var/www/magento1/index.php(87): Mage::run('', 'store')
  #15 {main}
  </code></pre>
  
  <p>config file etc/config.xml</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;
  &lt;config&gt;
      &lt;modules&gt;
          &lt;MyCompanyName_HelloWorld&gt;
              &lt;version&gt;0.0.1&lt;/version&gt;
          &lt;/MyCompanyName_HelloWorld&gt;
      &lt;/modules&gt;
      &lt;global&gt;
          &lt;blocks&gt;
              &lt;helloworld&gt;
                  &lt;class&gt;MyCompanyName_HelloWorld_Block&lt;/class&gt;                
              &lt;/helloworld&gt;
          &lt;/blocks&gt;
      &lt;/global&gt;
      &lt;frontend&gt;
          &lt;routers&gt;
              &lt;helloworld&gt;
                  &lt;use&gt;standard&lt;/use&gt;
                  &lt;args&gt;
                      &lt;module&gt;MyCompanyName_HelloWorld&lt;/module&gt;
                      &lt;frontName&gt;helloworld&lt;/frontName&gt;
                  &lt;/args&gt;
              &lt;/helloworld&gt;
          &lt;/routers&gt;
          &lt;layout&gt;
              &lt;updates&gt;
                  &lt;helloworld&gt;
                      &lt;file&gt;helloworld.xml&lt;/file&gt;
                  &lt;/helloworld&gt;
              &lt;/updates&gt;
          &lt;/layout&gt;
      &lt;/frontend&gt;    
  &lt;/config&gt;
  </code></pre>
  
  <p>layout file helloworld.xml</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt; 
  &lt;layout version="0.1.0"&gt; 
      &lt;helloworld_index_index&gt;
          &lt;reference name="root"&gt;
              &lt;action method="setTemplate"&gt;&lt;template&gt;page/1column.phtml&lt;/template&gt;&lt;/action&gt;
          &lt;/reference&gt;
          &lt;reference name="content"&gt;
          &lt;!--&lt;block type="core/template" name="helloworld" template="helloworld/helloworld.phtml"/&gt; --&gt;
              &lt;block type="helloworld/helloworld" name="helloworld.helloworld" template="helloworld/helloworld.phtml"/&gt;
          &lt;/reference&gt;
      &lt;/helloworld_index_index&gt; 
  &lt;/layout&gt;
  </code></pre>
  
  <p>Block class file HelloWorld.php</p>
  
  <pre><code>class MyCompanyName_HelloWorld_Block_HelloWorld extends Mage_Core_Block_Template {
  
  }
  </code></pre>
  
  <p>controlers/ indexController.php</p>
  
  <pre><code>class MyCompanyName_HelloWorld_IndexController extends Mage_Core_Controller_Front_Action {
      public function indexAction() {
          //echo "We're echoing just to show that this is what's called, normally you'd have some kind of redirect going on here";
          $this-&gt;loadLayout();        
          $this-&gt;renderLayout(); 
      }
  }
  </code></pre>
  
  <p>app/etc/module MyCompanyName_HelloWorld.xml</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;
  &lt;config&gt;
       &lt;modules&gt;
          &lt;MyCompanyName_HelloWorld&gt;
              &lt;active&gt;true&lt;/active&gt;
              &lt;codePool&gt;local&lt;/codePool&gt;
          &lt;/MyCompanyName_HelloWorld&gt;
       &lt;/modules&gt;
  &lt;/config&gt;
  </code></pre>
  
  <p>Please tell me where i missed the things in it. Thanks in advance..</p>