www and non www issue

I just reading Google webmaster article, I not understand why www and non www are not a same domain?
http://www.google.com/support/webmasters/bin/answer.py?answer=44231

Next question, should I redirect index file to root domain? e.g. redirect from
http://www.talented.com.my/index.php to http://www.talented.com.my/

What is the impact, if I not doing that?

 

well because Google consider them 2 url's like and domain.com these are two website's for Google bot and when Google bot crawl that type of site It considers duplicate website.

 

The only problem with having two different versions (www and non www) of your site is that the backlinks are watered down between each URL, suggest to do the redirect

 

Another question, what about redirect the index file to root domain?

 

It is same as www and non-www
You might found your pr and backlink are different if you not redirect them

 

No issue with in www and non www our site open both of them and also i check my back link with it.

 

Thank you very much, it help me understand the correct step to setup a good website.

 

It really doesnt matter either way, whether using www or not, it just matters that you choose one and go with that...If you do not specify which one for the webpage to direct to then you will be seen as having duplicate content. Start with one or the other and keep it like that for the duration of the site.