Following is a 100% safe and easy method to block a website in your system:

1. Type the following command in Run:

Windows Vista\XP:
Notepad %windir%\system32\drivers\etc\hosts
Windows 2000:
Notepad C:\WINNT\system32\drivers\etc\hosts
Windows 98/ME:
Notepad %windir%\hosts

2. Under "127.0.0.1 localhost" just add the site you want to block

Eg:
127.0.0.1 localhost
127.0.0.1 google.com
127.0.0.1 http://www.google.com/
127.0.0.1 quest.com
127.0.0.1 http://www.quest.com/
127.0.0.1 free-ebooks.net
127.0.0.1 http://www.free-ebooks.net/

3. Save the file and exit notepad.
4. Restart the browser and PC(Optional).

Now, you won’t be able to access those websites at all.……

Please Note:

In most cases, if your HOSTs file is too large, the DNS Client(a system service), will slow down the machine. To resolve this issue do the following:

• Run Services Editor(services.msc)
• Navigate to DNS Client and right click it ; Select: Properties,
• Now, Under Start-Up Type.
• Select: Manual, or Disabled (recommended)
• Click Apply/Ok and restart your PC.

Post Edited

Follow the following tut to block following contents using this host file:
- Ads
- Banner
- 3rd Party Cookies
- 3rd party page counters
- Web bugs
- Hijackers
- Unwanted Adware/Spyware programs
- X Rated Contents

http://www.itech7.com/HOWTO/NewbieBlocking-Unwanted-ParasitesSites-with-...