Below code Use for show previous/next link in product page:
open view.phtml file (app/design/frontend/base(or your theme interface)/default(your theme interface)/template/catalog/product/view.phtml)
past below code above <div class="product-view">
<!-- Product Navigation -->
<div id="product-navigation">
<?php // Previous and Next product links in product page
if ($this->helper('catalog/data')->getCategory()) {
$cat = $this->helper('catalog/data')->getCategory();
} else {
$_ccats = $this->helper('catalog/data')->getProduct()->getCategoryIds();
$cat = Mage::getModel('catalog/category')->load($_ccats[0]);
}; //missing ";" causes 503 error for validation service
$_product = $this->getProduct();
if(!$_product->getCategoryIds())
return; // Don't show Previous and Next if product is not in any category
$order = Mage::getStoreConfig('catalog/frontend/default_sort_by');
$direction = 'asc'; // asc or desc
$category_products = $cat->getProductCollection()->addAttributeToSort($order, $direction);
$category_products->addAttributeToFilter('status',1); // 1 or 2
$category_products->addAttributeToFilter('visibility',4); // 1.2.3.4
$cat_prod_ids = $category_products->getAllIds(); // get all products from the category
$_product_id = $_product->getId();
$_pos = array_search($_product_id, $cat_prod_ids); // get position of current product
$_next_pos = $_pos+1;
$_prev_pos = $_pos-1;
// get the next product url
if( isset($cat_prod_ids[$_next_pos]) ) {
$_next_prod = Mage::getModel('catalog/product')->load( $cat_prod_ids[$_next_pos] );
} else {
$_next_prod = Mage::getModel('catalog/product')->load( reset($cat_prod_ids) );
}
// get the previous product url
if( isset($cat_prod_ids[$_prev_pos]) ) {
$_prev_prod = Mage::getModel('catalog/product')->load( $cat_prod_ids[$_prev_pos] );
} else {
$_prev_prod = Mage::getModel('catalog/product')->load( end($cat_prod_ids) );
}
$more_url = $cat->getUrl();
$nxtname=substr($_next_prod->getName(),0,25);
$prvname=substr($_prev_prod->getName(),0,25);
?>
<style>
.prelinknav{float: left;width: 33%;font-size: 11px;text-align: left;}
.nxtlinknav{float: left;width: 33%;font-size: 11px;text-align: right;}
.catlinknav{float: left;width: 33%;font-size: 11px;text-align: center;}
.product-view{float: left;}
</style>
<div>
<?php if($_prev_prod != NULL): ?>
<div class="prelinknav"><a href="<?php print $_prev_prod->getUrlPath(); if($search_parameter):?>?search=1<?php endif;?>" ><span
style="font-weight: bolder;"><?php echo $this->__('<<< PREVIOUS') ?></span>(<?php echo $prvname; ?>)</a></div>
<?php endif; ?>
<div class="catlinknav"><a href="<?= $more_url; ?>"><span style="font-weight: bolder;">Back</span>(<?php echo $cat->getName() ?>)
</a></div>
<?php if($_next_prod != NULL): ?>
<div class="nxtlinknav"><a href="<?php print $_next_prod->getUrlPath(); if($search_parameter):?>?search=1<?php endif;?>"><span
style="font-weight: bolder;"><?php echo $this->__('NEXT') ?></span>(<?php echo $nxtname; ?>)<span style="font-weight: bolder;"><?php echo
$this->__('>>>') ?></span></a></div>
<?php endif; ?>
</div>
</div>
<!-- end pagination nav -->
now check in frontend product view page