customize of label "choose an option" of configurable product in magento

Step 1: Change in catalog/product/view/type/options/configurable.phml getProduct(); $_attributes = Mage::helper('core')->decorateArray($this->getAllowAttributes()); ?> isSaleable() && count($_attributes)):?>

getAttributeId(); $_attributeInfo = Mage::getModel('eav/entity_attribute')->load($_attributeId); $_attributeLabel = str_replace(' ','-',strtolower($_attributeInfo->getFrontendLabel())); ?>

decoratedIsLast){?> class="last">

getFrontendLabel() ?>

Step 2: js/varien/configurable.js replace line 171 = element.options[0] = new Option(element.config.label, '');

 Step 3: app/design/frontend/default/grayscale/template/catalog/product/view/type/options/configurable.php change this line: 'label' => 'choose a '.$attribute->getLabel(),