The rules are simple: Green color means you don't need to do anything (of course there could still be things you can do to get better performance). Yellow tells you that you should look into this, and guess what, red means that something is really bad.
- Sitespeed score are based on the rules (modified and enhanced Yslow rules): Over 90 is good, between 80-90 is not so good, and below 80 is bad, really bad.
- The number of requests: Below 25 is good, between 25-50 is something you should look into and above 50 is bad.
- The weight of a page: Below 1 mb is ok (but really too large for mobile), between 1-1.5 mb is something you should investigate & heavier is bad.
- The document weight: Below 10 kb is good (gzipped), between 10-15 is ok (but can be better) and above is bad. A small document is good for mobile.
- The number of stylesheets: One is good, more than five is really bad.
- The number of stylesheet images: Two is good, above four is bad.
- The number of images: 25 or less images is OK, below 40 is ok, and above is bad.
- The number of requests for a primed cache: 2 requests is good, else if not 90% of the request are cached, it is bad.
- The number of pages with the possibility of frontend single point of failure: 0 pages is good, everyhing else is bad. Excludes subdomains on the document domain from the spof.
- Average number of requests for static content without a far-future expiration date: 0 is good. More than 4 is bad. Google Analythics & Gaug.es is excluded from this.