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\!h check special price

$specialprice = $_product->getSpecialPrice();
$regular_price = $_product->getPrice();
$specialPriceFromDate = $_product->getSpecialFromDate();
$specialPriceToDate = $_product->getSpecialToDate();
$today = date('Ymd');

if (!empty($specialprice) && $specialprice < $regular_price){
    if($today >= date('Ymd', strtotime($specialPriceFromDate)) && $today <= date('Ymd', strtotime($specialPriceToDate)) || $today >= date('Ymd', strtotime($specialPriceFromDate)) && is_null($specialPriceToDate)){
        $_label = '<strong class="product-tag-mark label-sale">' . _('Sale') . '</strong>';
    }
}

\!h percent difference

<?php 
    $specialprice = $_product->getSpecialPrice();
    $regular_price = $_product->getPrice();
    $currency_symbol = Mage::app()->getLocale()->currency( $currency_code )->getSymbol();
    $specialPriceFromDate = $_product->getSpecialFromDate();
    $specialPriceToDate = $_product->getSpecialToDate();
    $today = date('Ymd');

    if (!empty($specialprice) && $specialprice < $regular_price):
        if($today >= date('Ymd', strtotime($specialPriceFromDate)) && $today <= date('Ymd', strtotime($specialPriceToDate)) || $today >= date('Ymd', strtotime($specialPriceFromDate)) && is_null($specialPriceToDate)):
?>
    <div class="price-box">
        <p class="old-price">
            <span class="price-label"><?php echo $this->__('Regular Price'); ?>:</span>
            <span class="price"><?php echo $currency_symbol; ?> <?php echo number_format($regular_price, 2,',',''); ?></span>
        </p>
        <span class="sale">-<?php echo number_format((100 - ( $specialprice / ($regular_price/100) ) ), 0); ?>%</span>
        <p class="special-price">
            <span class="price-label"><?php echo $this->__('Special Price'); ?>:</span>
            <span  class="price"><?php echo $currency_symbol; ?> <?php echo number_format($specialprice, 2,',',''); ?></span>
        </p>
    </div>
    <?php endif; ?>
<?php else: ?>
    <?php echo $this->getPriceHtml($_product, true) ?>
<?php endif; ?>