Using IP address in order to open a web page

Question

Hello all,
For example, if I want to open the page www.google.com, i simply write this address in the address bar, then I press enter, and I see the page of the google in my browser.
However, instead, if i write the IP address of the page www.google.com in the address bar (let's suppose it is 1.2.3.4), the page is not opened. In this case, I receive an error saying that "problem loading page". Why is this happenning? is that the expected result, or is google preventing it somehow? If the google is preventing that, what might it be doing? How can it detect it, and what can be the bad result of just using the IP address instead of writing "www.google.com" from the view of google?
note: google is just an example here. it is also not working writing the IP address in other web sites.
Thanks & Regards
hs

Answer 1

hi again,
i checked the firewall and browser settings, but i could not find anything..
actually, i also want to write the reason why i came across this problem. i am a student, and i read sth on the net recently. it was about what happens if other people catch the chance to modify the settings of your computer. it was saying that if you place a new setting in the HOSTS file, you can phish people in this way.
for example, here is the content of my HOSTS file:
# Copyright (c) 1993-1999 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
127.0.0.1 localhost
for example, add this line to the hosts file:
1.2.3.4 www.google.com
save the file, and close. later, if you write www.google.com on your browser, instead of google's page, the page having the IP address 1.2.3.4 will be open.
i tried this, but it didnt work. later, i also write the IP address on the address bar, it did not work again.
so, i hope someone can catch the reason here.
by the way, my OS is windows XP home edition.
thanks for all answers! :)