Not so much a conundrum as the use of Canonical links for SEO is well documented but my angle is, as usual a little bit different.
The setup: We have a secure extranet and recently added two sites that had existed for some time on the internet and had a fairly decent page rank (in google at least) they both retained a public page for a period of a few months to advertise the fact they had moved.
The Issue: Google bot had spidered the sites but came up against our login page so updated it’s title and description but decided the original url was of greater importance than the actual url of our login page. The killer problem concerns our single sign on solution that remembers the URL you click on. The sequence would be as follows:
- User searches for Forces Gateway (now Defence Gateway).
- Google displays the Title and Description of the Defence Gateway Page but retains the url of one of the two former public sites.
- User clicks on link and logs in.
- Single sign on directs user to original url and not to the Defence Gateway page.
The Solution: It was very simple, we added a canonical link to each page and within a few days google had the correct url matched to the title and description.
Key statements from the Google Webmaster’s Help pages
Why specify a canonical page?
It’s common for a site to have several pages listing the same set of products. For example, one page might display products sorted in alphabetical order, while other pages display the same products listed by price or by rating. For example:http://www.example.com/product.php?item=swedish-fish&trackingid=1234567&sort=alpha&sessionid=5678asfasdfasfd http://www.example.com/product.php?item=swedish-fish&trackingid=1234567&sort=price&sessionid=5678asfasdfasfd
If Google knows that these pages have the same content, we may index only one version for our search results. Our algorithms select the page we think best answers the user’s query. Now, however, users can specify a canonical page to search engines by adding a
<link>element with the attribute
<head>section of the non-canonical version of the page. Adding this link and attribute lets site owners identify sets of identical content and suggest to Google: “Of all these pages with identical content, this page is themost useful. Please prioritize it in search results.”
Is rel=”canonical” a suggestion or a directive?
This new option lets site owners suggest the version of a page that Google should treat as canonical. Google will take this into account, in conjunction with other signals, when determining which URL sets contain identical content, and calculating the most relevant of these pages to display in search results.
- Which Page is Canonical? (seomoz.org)