Since i couldn't find any appropriate answer to my specific question, I wanted to ask you.

I've read alot of things about the 301-redirect for moving pages and so on. A customer of mine has booked a new domain last year for better search results (he included his main keyword into the domain. Before he had only a domain with his business name, which had nothing to say about what he does).

I told him, that he should do a 301-redirect so he doesn't loose his position in Google and to redirect all new customers coming from the old domain to the new domain.

After about one year where his site hat a good amount of traffic the search results of Google for his keywords are getting more worse. Since he didn't maintain his website (no new content, bad content on all pages and so on) I assumed this would be the problem.

He gave his website to another company which also makes websites. They told him, that this 301-redirection is very bad for his website. They removed it, and also updated his content and the template so now he has the same meta keywords on every page (instead of the specific ones I put there before). He also removed the canonical-tag which I placed there to ensure no duplicate content.

What I am now afraid of is, that without this redirect Google now will find duplicate content and therefore kick him out of the index, which would be a nightmare, since most of his customers come over his website.

I need verification of the fact, that the 301 isn't bad but in fact the correct way of working with 2 domains. If possible with good sources I can point out to him since he don't wants to hear anything about this.

If someone also has a few words about the keywords and the canonical-tag I would really appreciate it!

Thank you very much!