If you ever used Safari version 3, you may see the cool progress bar that combined with the address bar. When you browse the web, you will see the loading progress in the address bar.
If you’re a FireFox user you can have the progress bar like that too. With Fission, a plugin that combine the address bar and loading progress bar into one.
Fission combines address bar and progress bar (Safari style). This makes the progress bar more visible and allows for a nice visual effect.
Link : More Info & Download
You can download more styles here