Les dejo una ayuda para bloquear paginas en Internet:

1º: Ir a C/Windows/Sistem32/drivers/etc.

2º: El archivo llamado "hosts" lo abren con Bloc de notas (si no les figura en "abrir con" se van a Inicio-Todos los programas-Accesorios-Bloc de notas).

3º: Una vez abierto escriben al ultimo la pagina que quieren bloquear (por ejemplo: 127.0.0.1 www.facebook.com)
y abajo ponen la misma pagina pero así 127.0.0.1 facebook.com
les quedara así:

# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

# localhost name resolution is handled within DNS itself.
#127.0.0.1 localhost
#::1 localhost
127.0.0.1 www.facebook.com
127.0.0.1 facebook.com

4º: Haz clic en Archivo-Guardar

Y LISTO!!!!!!!!!!!!!!!