When we purchase a domain name (for e.g. say domain.com), we actually get the ownership of both www.domain.com and domain.com
Even though we can configure both the above web links to show the same page and get associated to same hosting, there are couple of problems that come up:
- Browser does not share the cookies among them. So if a user logs in on domain.com and then switches to www.domain.com, he will not see himself logged in.
- SEO treats them as different domains and credibility of your web site divides into two halves, one for each of them.
That is the reason, you see every other sites live with one of them and redirects the other one to the one they use. For e.g.