Diaplay SKU On The Product Listing Page.
Step 1. Navigate to the /app/design/frontend/default/your_custom_template/template/catalog/product/list.phtml or Navigate to the /app/design/frontend/base/default/template/catalog/product/list.phtml open the file in the editor of your choice.
Step 2. Add the code below in the appropriate position where you want to display the SKU
<?php echo nl2br($_product->getSku()) ?> <?php echo $this->htmlEscape($_product->getSku()) ?> <?php echo $sku = Mage::getModel('catalog/product')->load($_product->getId())->getSku();?>
Diaplay SKU On The Product Description Page
Step 1. Navigate to the /app/design/frontend/default/your_custom_template/template/catalog/product/view.phtml or Navigate to the /app/design/frontend/base/default/template/catalog/product/view.phtml open the file in the editor of your choice.
Step 2. Add the code below in the appropriate position where you want to display the SKU
<?php echo nl2br($_product->getSku()) ?> <?php echo $this->htmlEscape($_product->getSku()) ?> <?php echo $sku = Mage::getModel('catalog/product')->load($_product->getId())->getSku();?>
Now refresh the browser cache and you have done.