Avoid duplicate content. Every good Search Engine Optimization expert will tell you that original content is the best way to succeed in your attempt to climb the slippery search engine slope. Copying content from elsewhere or syndicating the the same content to other sites can have an adverse effect your page rank.
Unfortunately, most websites inadvertently publish duplicate text. Consider your home page; is the same content available from different URLs?…
http://www.mysite.com/
http://www.mysite.com/index.html
http://www.mysite.com/index.php?sessionid=57
Few content management systems handle duplicate pages well. A URL rewrite engine, such as Apache’s mod_rewrite, can help but it is difficult to guarantee a unique addresses for every page. Google and the other search engines do their best to address non-malicious duplication, but you can never be certain that your website has not been downgraded.
The duplicate content problem has finally been resolved with Google’s new canonical element. Web developers can indicate their preferred page URL using a new <link> tag in the HTML <head>. For example:
<link rel="canonical" href="http://www.mysite.com/" />
Note:
- The canonical URL must be on the same domain, although sub-domains such as www.mysite.com and products.mysite.com are permitted.
- Relative path names are handled and Google will resolve URLs to any path set by the page’s
<base>link. - The preferred URL does not need to contain an exact replica of the original page content. Google will permit slight differences, such as the order of a list of products. However, it is certainly advisable to avoid that situation where possible.
- Google will follow canonical chains, but recommend that a single valid URL is specified for the best results.
Further information and instructions are available at the Google Webmaster Central Blog. The tag is being parsed by the GoogleBot now. Both Microsoft and Yahoo have agreed to the proposal; they are likely to follow shortly.
Have you experienced page rank problems owing to duplicate content within your site? Will the canonical element assist with your SEO effort?
Craig BucklerCraig is a freelance UK web consultant who built his first page for IE2.0 in 1995. Since that time he's been advocating standards, accessibility, and best-practice HTML5 techniques. He's created enterprise specifications, websites and online applications for companies and organisations including the UK Parliament, the European Parliament, the Department of Energy & Climate Change, Microsoft, and more. He's written more than 1,000 articles for SitePoint and you can find him @craigbuckler.
