Early data from leading independent search marketing specialist and technology firm Greenlight, reveals big winners and losers, visibility-wise, from Google’s Panda algorithm update – designed to improve Google’s ability to detect and devalue “low quality content”, which it has now rolled out across all English language websites.

As soon as Panda was released in the US, Greenlight built a sample keyword set and started tracking visibility for this keyword set on Google.co.uk on a daily basis.

Greenlight’s early data reveals winners are largely made up of well known news sources such as The Guardian, The Telegraph, Yahoo.com, Times Online and The BBC, along with YouTube and a couple of other sites.

Meanwhile, big losers appear to include article and content directories such as HubPages and Ezine Articles, review sites like DooYoo.co.uk, “how too” sites like Videojug and eHow.  Most devastatingly of all, another review site, Ciao, has lost 99% of its search engine visibility in Google.co.uk.

“Naturally in an algorithm update of this scope, there have been numerous smaller niche sites that have both gained and lost from Panda, many of which would appear in the table below if we focus only on pure percentage gains or losses in reach”, say Adam Bunn, Director of SEO (search engine optimization) at Greenlight.  “Whilst the data is available, we feel the most immediately interesting stories are to be found in the fortunes (or misfortunes) of the bigger, more well known sites that appear in the list.”

Greenlight notes the effects of big algorithm updates tend to last a while, with ranking fluctuations occuring for several days or even weeks.  Given this being early data, Greenlight will be following up once things have had a chance to settle down, to see if anything has changed.