Standard FF may do what you want, but I use TMP to fancy up my browser. It lets you easily change the font color and features of unviewed tabs, read tabs, the active tab, etc., along with lots of other stuff. I've never tried to do these things with bare FF.

Beware that it seems to excite a memory leak in FF if you use the "Session Restore" feature (but FF's own crash protection stuff doesn't seem any better). If you restart your browser every day, it's not an issue either way.

[link|http://tmp.garyr.net/|http://tmp.garyr.net/]

HTH.

Cheers,
Scott.