The Hosts file contains the mappings of IP addresses to host names. This file is loaded into memory at startup, then Android checks the Hosts file before it queries any DNS servers, which enables it to override addresses in the DNS. This prevents access to the listed sites by redirecting any connection attempts back to the local (your) phone. Another feature of the HOSTS file is its ability to block other apps from displaying ads (not all).
How to install..
transfer hosts file to the tools folder of your sdk installation
open terminal with android connected and adb drivers installed
adb push hosts /system/etc
..or simply use Root Explorer
You are now protected against 14,714 ads, banners, sites and 3rd party Cookies
works on any 1.5 ROM, not sure if 1.6, 2.0 or 2.1 since i only use cupcake