We detected the following sites were using Rainbow
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.
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.
Dedicated Content Management System Detection