Accessing a shared hosted website through it's IP

[Unhumanje]

First things first, I googled this however I didn't find anything. To be honest, I am not quite sure what my key words should be.

What I am trying to achieve is access a site through it's IP address rather than its URL. For example - I won't open google with google.com, but rather with http://74.125.79.99 . So far so good. However, most sites have shared hosting. So that 1 IP address is hosting multiple web pages. From what I found out from google and from some personal 'tests' they mostly work on the principle:
http://IPaddress/~user , where user is usually 8 letters/digits.

So here is where my question stands - is it possible and if yes, how can I find the "user" so that I can access the site this way?



Thanks in advance for any input.

EDIT:

Sorry for the links, didn't realise they were inappropriate.

However, until when will all my actions be moderated? This topic took like 5 days to get approved :/ I almost forgot I posted it. And due to that delay the topic is now on page 2 (despite actually being approved yesterday/today) where almost no one will look :|