It's called mouse wheel, u can use it to scroll down the page, to find what you are looking for...

Power management

* Talk-time (Maximum):
o GSM up to 6.3 hours
o WCDMA up to 4.3 hours
* Standby time (Maximum):
o GSM up to 278 h
o WCDMA up to 250 h
* Active online usage (Maximum): Up to 1 day
* Continuous browsing time (Maximum):
o WCDMA up to 5.5 hours
o Wi-Fi up to 8 hours
* Video playback time (Maximum): Up to 5.6 hours
* Music playback time (Maximum): Up to 24.5 hours

Regarding battery life itself, people say you can charge your lithium battery 1000+ times, but i guess it dependes on how good you take care of your battery. My N95 8GB battery is 3 years old and still in excellent shape.