Is SeoMOZ Crawl Diagnostics wrong here?

[Webdannmark]

We've been getting a ton of critical errors (about 80,000) in SeoMoz' Crawl Diagnostics saying we have duplicate content in our client's E-commerce site. Some of the errors are correct, but a lot of the pages are variations like:

www.example.com/productlist?page=1

www.example.com/productlist?page=2

However, in our source code we have used rel="prev" and rel="next" so in my opinion we should be alright.

Would love to hear from you if we have made a mistake or if it is an error in SeoMoz.

Here's a full paste of the script:

[Dr-Pete]

Just a minor clarification - you can use both rel=prev/next and rel=canonical, IF you have something like search filters. Then, the canonical would point to the unfiltered current page and the rel=prev/next would point to the filtered paginated pages. Yeah, I know, that made a lot of sense. Let's say your page is:

http://example.com/stuff?page=2&sort=price

...then you might have

It's more than a little confusing.

Definitely check out that JavaScript issue, though - it might be that bots aren't seeing what people are seeing, and that could be very dangerous.

[LynnPatchett]

Hi,

In regards the rel=next you are absolutely right, I must have overlooked it or just searched for the prev tag. So yes as far as proper implementation of the prev/next in that respect it is correct and please ignore that last part of my first post!

Turning of javascript is instructive to see all those tags on their individual page and helps clarify what exactly is being outputted and when without the dynamic loading, providing you don't miss a rel=next tag that is really there

[Webdannmark]

Hi Lynn,

Thank you very much for your answer / analysis! As you said "It is a bit confusing" and I will just read your answer a couple of times...

I will grant your answer "Good answer" for you thorough analysis! I think it is spot on with the double "next/prev" and "rel=can" tags.  I do have one remark. You said:  When I turn off javescript, I get this:

In my opinion this is alright, because it shouldn't have a "prev" as this is the initial page.

[LynnPatchett]

Hi,

I had a look at what I assume is the site and I think you have a combination of things going on that is likely causing confusion (to you, to the moz bot, probably to google too!)

Firstly, it is not recommended to use rel prev/next and rel canonical on the same page. With that what you are effectively doing is only indexing the first page of the results since all the other pages rel canonical back to the first one. If you have a 'view all' type page then you could rel canonical all of the paginated pages back to this one and you would not need to use the prev/next tags at all. It is also possible that your use of relative canonical links in combination with the above is also causing confusion, usually best to use absolute urls if possible.

Beyond that, the site dynamically loads more products as you scroll down the page which also results in the url changing to hoeretelefon/? for ALL the pages. If that is a problem or not depends on how it is coded and how the google and seomoz bots are deciding to parse the page, but it certainly adds another potential area of complexity to the issue.

Lastly, if you browse the site with javascript turned off you can see something odd in that the initial page /elektronik/baerbar-lyd/hoeretelefon has no prev/next OR canonical tag but has a link to /elektronik/baerbar-lyd/hoeretelefon?page=1 on which you find prev/next and canonicals back to the non paginated version. So you are basically skipping the pagination setup that goes from the original to the page=1 (but also giving a canonical back to the original page).

Phew! It is a bit confusing. I would recommend deciding on if you want to go with prev/next or canonical in the first place and take it from there. I would think that if you have the ability to canonical to a 'see all products page' then this might be the best way to go since it should theoretically take care of any issues the dynamic loading is causing also.

Hope that helps!