More odd looking links on the BBC Sport site - why isn't the link a proper one and why is carrentals.co.uk designated as a sport site by the BBC?

rel=canonical is a way to tell Google which the primary version of a URL is. It's handy if you have substantially the same content on several URLs - perhaps because you have a shopping site and allow users to sort a list of products by price or name, and this is reflected in the URL.

Adding this meta tag used to work only on the same domain.

But Google has announced today that it will support rel=canonical across domains - ie if you have the same content on more than one website, you can tell Google which is the main version you'd like it to index.

The furore over Jan Moir has thrown up several interesting SEO issues. Here's a basic one - how should you link to something you detest?

The problem with linking
Put simply, Google counts a link to a ...

As part of the fuss over Jan Moir, the Daily Mail ended up changing the headline and the URL of its story and 301 redirecting the old URL to the new one. I wondered what would happen to the Sidewikis written on the original URL. The answer: the Sidewikis remain with a message saying they were originally about a previous URL.

You may not know it, but the www version of your website is not the same as the non-www version.: yourdomain.com/page is NOT THE SAME PAGE as www.yourdomain.com/page. It's treated as a different URL by search engines, for instance. And if someone leaves off the www (on a link or when they type a URL), they may not get any page at all unless you've set your server up right.