"...the Hosts file is like an address book. When you type an address like www.yahoo.com into your browser, the Hosts file is consulted to see if you have the IP address, or "telephone number," for that site. If you do, then your computer will "call it" and the site will open. If not, your computer will ask your ISP's (internet service provider) computer for the phone number before it can "call" that site.
Most of the time, you do not have addresses in your "address book," because you have not put any there. Therefore, most of the time your computer asks for the IP address from your ISP to find sites."
What is a Hosts file? MVPS.org has a Hosts file that you can download and install. It includes a BAT file that renames the old file before it saves the new one. Hosts
"Important Notice - 2K/XP Users
In most cases a large HOSTS file (over 135 kb) tends to slow down the machine. This only occurs in W2000 and XP. Windows 98 and Windows ME are not affected.
To resolve this issue (manually) open the "Services Editor"
Start>Run (type) "services.msc" (no quotes)
Scroll down to "DNS Client",
Right-click and select: Properties
Click the drop-down arrow for "Startup type"
Select: Manual, click Apply/OK and restart.
If you want to see Google AdSense entries, you may want to edit the MVP list. One of the entries is: 127.0.0.1 adwords.google.com #[Gmail ads]
Plus other Google entries.