"You can learn a lot about a site when you monitor its network connections when you connect your browser to it.Source: gHacks Tech News
"You may see connections to third-party sites, ads, web analytics scripts and a lot more just from that.
"These resources are often essential for a site's functionality, and blocking them may break part or all of a site.
"There are two concerns that Internet users may have when it comes to the use of these content delivery networks: privacy and speed.
"Speed is easier to explain. While it is often faster to use a CDN for resources than a locally hosted version on the site's server itself, it still means having to make a connection to the CDN in first place. That's not as fast as making these resources available locally on the user's computer. ..."
Decentraleyes for Firefox loads CDN resources locally