How does this URL has something before www?

Question

I've never seen that before! How's does that works? I know ICANN now allows custom domain names, but it's before www! I've tried to add another www before welcome and it returned 404.

Answer 1

www is not something special. There is no difference for server between www or www1 or welcome. There are websites without www at all. Actually www is subdomain and you can create two different websites: one on www and another without.

Answer 2

RFC 1035 defines the grammar below. Also, you may want to see this wikipedia article.

<domain> ::= <subdomain> | " "

<subdomain> ::= <label> | <subdomain> "." <label>

<label> ::= <letter> [ [ <ldh-str> ] <let-dig> ]

<ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>

<let-dig-hyp> ::= <let-dig> | "-"

<let-dig> ::= <letter> | <digit>

<letter> ::= any one of the 52 alphabetic characters A through Z in
upper case and a through z in lower case

<digit> ::= any one of the ten digits 0 through 9

Note that while upper and lower case letters are allowed in domain
names, no significance is attached to the case.  That is, two names with
the same spelling but different case are to be treated as if identical.

The labels must follow the rules for ARPANET host names.  They must
start with a letter, end with a letter or digit, and have as interior
characters only letters, digits, and hyphen.  There are also some
restrictions on the length.  Labels must be 63 characters or less.

For example, the following strings identify hosts in the Internet:

A.ISI.EDU XX.LCS.MIT.EDU SRI-NIC.ARPA

Answer 3

It's a 4th level subdomain, where www of www.example.com is a 3rd level as example is a sub of .com.

So, subdomains can do down 127 levels, such that my.desktop.www.example.com would be an valid URL with in thise case the www, in the middle.

Look at something like a traceRT anything, you might see something like dsl123.sfv.la.example.com (or whatever), point is, there are many cases of multi level subdomains, with or without the WWW - Another example might be mail.phx.example.com, a mail server for the phoenix office of a company.

Answer 4

People can put whatever they like in subdomains, then tell the server to "treat example.com.au the same as www.example.com.au"

therefore you could have a "real" URL of, eg:

www.abc.www.example.com

then tell the server to allow:

abc.www.example.com

This may be what you're seeing...