Im unable to use internet on my blackberry 8100 with airtel connection

Check whether you are getting EDGE/GPRS in upper case.Have you activated BB services,if you have already activated BB services there may be a network issue also and check whether there is a check mark in blackberry internet services(Menu-Options-Security Options-Firewall-BlackBerry Internet Service)if there is a check mark on it remove it.If you are using BIS check the default browser is Internet Explorer of if you are a BES user default browser is Blackberry Browser.Menu-Options-Advanced Options-Browser-Press menu-change Options-select the browser according to the service.