What do you mean by Canonical Issues? How We can resolve?

[erieki]

Canonical Issues is something that occurs if you have same content present on multiple pages with different URLs. This can be resolved defining rel=canonical on both pages stating which page should be considered.

=> How to resolve it

The best and most effective way to resolve the canonical issue is with a permanent 301 redirect. This can be implemented in a number of ways, as detailed below. Depending on what server your website is hosted on will determine the method which you use to implement a redirect.
In addition to this it is worth also logging into Google Webmaster Tools and set-up two profiles for your domain; one with the www. prefix and one without. Then go to Site Configuration> Settings> Preferred Domain and choose which domain you would like Google to use.