The market share for Ckan decreased by 0.0015 percentage points (from 0.002% to 0.0005%) for all sites, more than any other segment during the same period of time.
A CMS will sometimes include a meta tag within the html of each page. This is usually a "generator" tag like <meta name="generator" content="What CMS" /> but could also be "application-name", "Powered-By" or anyting else the CMS creators decide to use.
Headers
HTTP headers can provide some of the best clues about a site's CMS. The values of set-cookie and x-powered-by headers are the most common and easiest to find.
Versions
In addition to detecting the CMS, in some cases we are able to accurately detect which version of the CMS is being used.