WebMetronome makes it easy for you to practice your music. It's got a clear display, accents on any beat, a wide range of tempos, and an easy-to-understand interface. You can get higher-quality versions on iPhone or Windows and Mac. These apps are more precise and allow you to use the Metronome without an Internet connection.
v1.2 [Nov 15, 2011]
* tap-in beat, by clicking the big numbers (shortcut key x)
* added tuning window, for common notes
* added practice timer
* added full screen, resizeable window
* added volume control
* added "snap to traditional BPM values" setting
and a few other minor tweaks. enjoy!