manage error measage

-- HikaShop version -- : 2.3.4
-- Joomla version -- : 2.5.8
-- PHP version -- : 5.5

Hi

I want the "consumer" see the link to a product in the menu but register before view the product content. So the product has ACL registered but the link has no ACL rule .
So by default in the standart version, hikashop redirect to the message/link "HikaShop , Joomla!® Shopping Cart Extension" .
Is there a way to custom( manage) this default message and add more information to the default message ?
In my case the message should be " you can't have access to this product click on this link to register " .
Thank's

Yes i remove all the content in error.php and redirect to a webpage article .