Canonical URLs is very significant factor in terms of SEO, each website need to have canonical URL attributes for search engine prospective. If this attribute are not available then you might be facing the problem of duplicate content i.e. www. and without www. Domain name considerable different domain name search engine.
You know, now days Google penalizes the websites if your website are having “duplicate content”, you have been observed sometimes you have two URLs that refers same page i.e.http://abc.com/coursesl.html and http://abc.com/mba/coursesl.html actually might refer the same product page. But in technical terms these URLs are different. On the other hand Google thinks there are two pages having duplicate content. That’s why canonical URLs are being used to prevent from such issue. If you use Canonical URLs, Google must index the site even of the one used to access the page.
You need to be inserted at the top index.asp or default to asp file to get non WWW version redirected to www version of home page or index page: -
