This trick will work for Windows XP, Windows Vista and Windows 7. Using this method will block access to the website from all browsers installed on the system.
Open Run box from Start menu or directly by pressing Win+R
Copy and paste this line in the Run box and press OK.
The Host file will open with notepad. Now go to the last line of file and press enter and type the line as below:
You can add more websites in a similar fashion by entering a new line and typing the same thing with another website name.
Now save the file by pressing Ctrl+S or by going to menu File=>Save. Close the file.
You have done.
Follow the same procedure to unblock the website again by removing the concerning line from the file.