A quick method of getting an overview into the amount of quality content on a website is to check how many of its pages have been relegated to Google's Supplemental Index.
This useful information helps gauge how much of the website is performing, and how much improvement work is required. While not an exact science, certain search queries can give us the number of quality pages, and therefore supplemental pages, that a particular website has. The data has always tended to correlate pretty well with the amount of pages being visited from search.
The Star Query
I'm not sure if this page quality query goes by some other name in SEO circles, and I've personally not seen or read much about it. To me, it's always been known as the star query and I'll often pull it out when auditing a client website to give a overview, something a little bit like, well exactly like in fact, the chart below:
The star query consists simply of adding a star '*' to the end of a site search, which returns only the quality pages on that site. For example:
So the BBC has a total of 19,700,00 indexed pages, with 9,520,000 'quality' pages. Take one from the other and bingo; you've got the amount of pages in the supplemental index.
Of course, we have to take the figures with a pinch of salt, but nonetheless it's a useful snapshot.
For anyone unsure of exactly what the supplemental index is, they are the omitted results that can be seen at the end of the normal listings.
In order to show you the most relevant results, we have omitted some entries very similar to the XX already displayed.
If you like, you can repeat the search with the omitted results included.
These results are have been deemed to be of low importance and usually contain duplicate content, pages with low PageRank, complex URLs and other nasties.
In 2007, Google officially changed their handling of these pages and announced they were entwining them with the main index, narrowing the distinction. That being said, the star query continued to tie up nicely with the amount of landing pages from search. That is until very recently.
I've started to see a bit of a shift in the query's results, which now only seems to return decent results for some sites, invariable the larger websites around such as the BBC. Client sites that returned good results with the star query just a few months ago no longer to do so:
Receptional's site is the same, with not even the homepage returned as a 'quality page'.
Either Google's handling of the query has changed, or a lot of pages across a lot of domains have been demoted. Does anybody else use the query and noticed a change?