What does "Blocked" really mean in the Firefox developer tools Network monitoring?

firefox, firefox-developer-tools, network-monitoring

Solution

We changed the Firefox setting (about:config) 'network.http.max-persistent-connections-per-server' to 64 and the blocks went away. We changed it back to 6. We changed our design/development method to a more 'asynchronous' loading method so as not to have a large number simultaneous connections. The blocks were mostly loading a lot of png flags for locale settings.

Problem

The timing section of the Firefox Network Monitor documentation, "Blocked" is explained as: Time spent in a queue waiting for a network connection. The browser imposes a limit on the number of simultaneous connections that can be made to a single server. In Firefox this defaults to 6 Is the limit on the number connections the only limitation? Or is the browser blocked waiting to get a connection from the OS count as blocked too? In a fresh browser, on a first connection, before any other connection is made (so the limit should not apply here), I get blocked for 195 ms. Is this the browser waiting for the OS? Was does "Blocked" mean here?

Original source