Hi Nicolas,
I had just finished typing this message when I received your reply via email, but I just found out what it is.
After hours of searching and enabling and disabling possibly relevant plugins and components, it was finally a problem in Hikashop -which I had done myself by the way-.
I found out when I tried another template and the noindex tag was gone in the source code.
So I downloaded the template I use to my desktop and searched it with Notepad++.
It turned out that it was in a code I put in listing_img_title.
<?php
if($this->row->meta_noindex == 'true'){
$doc = JFactory::getDocument();
$doc->addCustomTag( '<meta name="robots" content="noindex" />' );
}
?>
I have created a custom product field with meta_noindex and default value "false".
The reason I did dis is that every month I have special offers with characteristics that I place in option products;
This message contains confidential information
In those option products I set the custom meta_noindex field to “true” because these products are removed after a month so I don't want them indexed by Google to prevent 404 errors.
And all categories/product listing pages that contain such a product offer are marked in the source code as noindex. That also explains why one product page has it and the other does not.
Once I removed the code from listing_img_title the noindex tag was also gone from the source code.
So I'm really glad the issue has been resolved, but I'd still like those option products not to be indexed by Google because they're only valid for one month and then I'll remove them again.
Is there another way to prevent these options products from being indexed by Google?