Rel= Canonical

[tiffany1103]

Almost every one of my product has this message: Rel Canonical (Using rel=canonical suggests to search engines which URL should be seen as canonical. )

What is the best way to correct this?

[GPainter]

I'm a bit confused so you are saying all of your products has a canonical tag or none of them?

The tag is great if you have duplicate content, it tells search engines the original content location and thus will give juice to that. If you don't have duplicate content you don't need to worry.

[tiffany1103]

Under Crawl Diagnostics --> Site Information --> Total Issues (1) --> Actions (View Issue)

Then, it will tell me the URL and the issue (rel=canon.).  I am not sure how to fix it. Hope that explains.

[GPainter]

I assume you mean Search > Crawl Diagnostics > Issues overview

There is a note telling you that you have a canonical tag which is fine (a black tag) this is more informational and shouldn't worry about it.

When to worry - If you have duplicate content.

edit also assuming this in Moz reports