URL canonicalization

hello guys,

How important is URL canonicalization?

I am planning to redirect URLs, domain.com and domain.com/index to www.domain.com. Is this very important to do?

Very Good question from the point of view of SEO.

URLs can be written in different ways like :-
1) www.example.com
2) example.com
3) www.example.com/index.html
4) www.example.com/default.asp

All the url written above will give us the same result means the same page. SE's see all the pages differently means in the eye of crawlers all the urls are different this means they usually assume it as content duplication so this should be avoided by using 301 Redirection.

For more information you can see what Matt Cutt have to say regarding it.

ok that means it is still in practice and i can go ahead and do 301 redirect.
I heard it is a old seo practice now not is use. so i was skeptical.