MAC (Media Access Control) address is a unique identifier assigned to network interfaces for communications on the physical network segment? (wikipedia). It is stored in the network interface card by the manufacturer.
The MAC address consists of a series of six pairs of numbers and letters separated by dashes. It’s a base-16 value (also called hexadecimal) [...]

Standard mozilla firefox browser does not have google pagerank toolbar. This toolbar shows you the google pagerank of the current url. If you need this tool you should install it by yourself. The tool comes as add-ons to mozilla firefox browser.
You can install the google pagerank tool from here.
If you have successfully installed google pagerank [...]