一、什麼是hosts文件?
hosts是一個沒有擴展名的系統文件，其基本作用就是將一些常用的網址域名與其對應的IP地址建立一個關聯“數據庫”，
當用戶在浏覽器中輸入一個需要登錄的網址時，系統會首先自動從Hosts文件中尋找對應的IP地址，一旦找到，系統會立即打開對應網頁，如果沒有找到，則系統再會將網址提交DNS域名解析服務器進行IP地址的解析，如果發現是被屏蔽的IP或域名，就會禁止打開此網頁!
二、Win7的hosts 默認文件
文件地址：C：WINDOWSsystem32driversetchosts
默認裡面的內容如下：
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# 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
