If a site has Certified Metrics instead of estimated, that means its owner has installed code allowing us to directly measure their traffic.
The more traffic a site gets, the more data we have to calculate estimated metrics.
There is not necessarily a link between the upstream site and this site.
The "Sites Linking In" count shows the number of sites that Alexa found that link to this site.
This is quite a good result, as only 30% of websites can load faster.
HTML content can be minified and compressed by a website’s server.