What is the different between http://www.example and http://example.com

[idandone]

Hi Guys,
What is the different between http://www.example.com and http://example.com?
I'm looking for technical explanation and also want to understand the SEO affects.

In addition, what happen when I promote a site with inbound links to
"http://www. example . com" and "http:// example . com".
Does the link juice drain to one URL or two different ones?


Thanks

[incrediblehelp]

Pick one as your main domain that you want to internally link to and you want external websites to link to. Usually people pick the www one. Then 301 redirect the non-www to the www.

You do this to avoid duplication/canonicalization issues with the search engines.

[sharonjackson]

Search engines see
www.yourdomain.com and
yourdomain.com

as TWO DIFFERENT pages. I use an .htaccess direction to send the non-www one to the www one.

i.e.

RewriteEngine On
RewriteCond %{HTTP_HOST} ^yourdomain.com
RewriteRule (.*) http://www.yourdomain.com/$1 [R=301,L]
ErrorDocument 404 http://www.yourdomain.com

The only place this does not work well is on older servers (?) where the host directory is
http_docs or where a previous webmaster has built some weird configuration. Maybe someone else can respond to that.

[usmanz]

I never bothered about that and I never had any issue with search engines.
Aren't search engines smart enough to know yourdomain.com and www.yourdomain.com are same?

[sharonjackson]

Well, I have done studying on this specific issue and that is what I learned.

It is a simple enough fix. If you don't believe me, perhaps you could believe the expert who has already commented here...the guy with over 7000 posts.

I would probably listen to him.

[SemAdvance]

I never bothered about that and I never had any issue with search engines.
Aren't search engines smart enough to know yourdomain.com and www.yourdomain.com are same?

No

The issue is known as a canonical URL issue. When Google sees links to your site in various forms it stores those links and indexes the pages it finds by following those links.

They see http://www.examplesite.com and all the links to it and scores those links and assign PageRank

Next they see http://examplesite.com and all the links to it and scores those links and assigns PageRank

They can also see www.examplesite.com and all the links to it and scores those links and assigns PageRank

As you can see the site then appears as duplicate content and also having this error dilutes your sites true PageRank.

You may not have noticed a problem but that is often due to lack of a very competitive category or competitors with little or no SEO work done.

People forget there are 1,000,000,000s of other sites beyond their own backyard, and what effects one, may or may not effect another.

[amnesia]

idandone, DNS works like this:

<host>.<domain>.<tld><root>

Where <root> is a dot (usually left out), <tld> is your top-level domain (.com, .net, etc), domain is your actual domain, and <host> is a machine in that domain. Lookups are done by finding authorative servers from right to left. A fully qualified example would be:

Example Web Page. or accounting.example.net.

'www' - not by rule but by tradition - is classically the machine name given to a domain's web server (just as the mail server is classically named 'mail', ftp server is 'ftp' and so on). If the sysadmin had been cheeky and named the server 'fart', you'd access the site via http://fart.example.com/ and Example Web Page would be an invalid lookup (unless aliased).

The domain itself with no host (example.com) should really not have a record associated with it, and some hardcore DNS geeks would tell you it is bad form to do so. Technically a lookup on 'example.com' should return an error. But it's very common these days to alias the domain to the web server for convenience.

Whether the search engines treat them as separate sites or not is probably determined by whether they used a CNAME or an A record in the domain's resource file, and also probably varies from bot to bot. It's doubtful that the protocol is taken into consideration as SemAdvance suggested, but I suppose some very poorly written bots might include it.

But the bottom line is it certainly makes no sense to have multiple URLs point to the same resource though, and you should definately use URL rewriting to ensure all of your URLs become something consistent when they are accessed.

[amnesia]

RewriteEngine On
RewriteCond %{HTTP_HOST} ^yourdomain.com
RewriteRule (.*) http://www.yourdomain.com/$1 [R=301,L]
ErrorDocument 404 http://www.yourdomain.com

The only place this does not work well is on older servers (?) where the host directory is
http_docs or where a previous webmaster has built some weird configuration. Maybe someone else can respond to that.

It has nothing to do with having an older server and the document root is completely irrelevent. The only time this won't work is if a) you aren't running Apache, and b) you don't have mod_rewrite installed.

More importantly that rewrite is pretty sloppy and leaves a lot of holes, here's a better way:

RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.example\.com [NC]
RewriteCond %{HTTP_HOST} !^$
RewriteRule ^/(.*) http://www.example.com/$1 [L,R=301]

[carol]

Great, but what if you are on a shared Windows server? Are we out of luck??

[ron angel]

Pick one as your main domain that you want to internally link to and you want external websites to link to. Usually people pick the www one. Then 301 redirect the non-www to the www.

You do this to avoid duplication/canonicalization issues with the search engines.

I have found the simple way around this is to use the full
SS Richard Montgomery matter on all internal & external links always.