Will canonical tag on non-copy content harm my site?

[JonnyGreenwood]

Days ago I added rel=canonical tags on my site.

For the post pages, I add canonical tag on both post page (www.exmample.com/post.html) and comment page (www.exmample.com/post-sms.html), all the canonical tags are pointing to post page, but in fact there are only comments on the comment page.

For product pages, I add the canonical tags on both product info page, download page, and order page, all of them are pointing to the info page, while in fact they are displaying different content.

I no-indexed the comment page, download page, and order page for a long time.

After I added the canonical tags, the traffics dropped (not hugely but slowly and steadily). Are my actions harming my site?

Is this a normal flux after adding codes to the entire site, or it's the bad outcome for wrong SEO actions?

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PS: I can't change the site structure, so it's not possible to combine post and comment pages into one, so do the product pages.

Thank you guys

[AlanMosley]

First I would not no-index any page, as you then have links that point to those pages pouring link juice into the abyss. If you must no-index a page use the meta no-index,follow this way the links will be followed and link juice can flow back into your site.

If these pages are not duplicates, then why canonical?

But seeing you have, I cant see no harm in what you have done. it would be good to ge a url so we can check that the canonicals are correct

[JonnyGreenwood]

Alan thanks for reply.

I no-index those pages via meta no-index, not in robots.txt or sitemap.

I have modified the canonical tag in download page from pointing to product page to the download page itself. Now all the pages get the canonical tags which point to the page itself, not to another page.

About 12 hrs passed, things begin to take a favourable turn, i am seeing organic traffics and page views are coming back to normal level.

[AlanMosley]

Good to hear.

As for the meta noindex, you ned to use <meta name="robots" content="noindex, follow">

So that the links are followed and return link juice.

Pointing a canonical tag to itself, has no use. in fact Bing doesn't like it. See quote, the whole page is a good read

Something else you need to keep in mind when using the rel=canonical is that it was never intended to appear across large numbers of pages.  We’re already seeing a lot of implementations where the command is being used incorrectly.  To be clear, using the rel=canonical doesn’t really hurt you.  But, it doesn’t help us trust the signal when you use it incorrectly across thousands of pages, yet correctly across a few others on your website.

A lot of websites have rel=canonicals in place as placeholders within their page code.  Its best to leave them blank rather than point them at themselves.  Pointing a rel=canonical at the page it is installed in essentially tells us “this page is a copy of itself.  Please pass any value from itself to itself.”  No need for that.

http://www.bing.com/blogs/site_blogs/b/webmaster/archive/2011/10/06/managing-redirects-301s-302s-and-canonicals.aspx

[Dr-Pete]

Like Alan, I have my doubts about whether the canonical tag is the best bet here. If the download/order page are down the click path from the product info page, I think it's ok to META NOINDEX,FOLLOW those pages (they have little or no search value). I generally wouldn't noindex and canonical a page - it's a mixed signal, and if things go wrong, you won't know why.