How can I do for my site?

[anfeng3]

Hi web experts, this is the first time to post a new thread here, and don't know whether can post the link of my site here or not.

I have a old website built on 2012, it has been changed entirely from Aug. to Oct. of last year, except for the domain, the host, frame, content, urls, title tags of every page, product pictures, meta descriptions and keywords, have been changed, the purpose is for mobile friendly. Here please let me have two problems:

First, after the new virsion was published on the internet in Nov. if searched by site:www.domain.com on Google, there're so many SERPs of old webpages which appeared 404 if you open them.

Second, the SERPs of new webpages and old one, some of the title tags were changed by Google.

How can I do now?

[htmlbasictutor]

To get rid of the 404s - The person who redid the site should have used 301 permanent redirects to fix the missing pages.

Regarding the titles - Both major search engines reserve the right to display whatever title and/or description they feel best suits the user's search.

[lucy24]

The person who redid the site should have used 301 permanent redirects to fix the missing pages.

If the site has been fully redesigned from the ground up, a more appropriate response might be a 410 with accompanying nice 410 page for returning human visitors.

some of the title tags were changed by Google.

Yes, Google does this. There have been many threads about it and there's not a thing you can do.

[mack]

Welcome to WebmasterWorld . There is never going to be a flawless method of entirely re-building a site. There will always be something that doesn’t quite work out as you intended. The key here is to ensure the site works well for a visitor who is using your site now, and to ensure you catch as many users landing on 404 pages etc. there will also be a little bit of collateral damage, but you now have a site that will be better suited to the future and can serve your users better.

Mack.

[eurohttp]

If your site is programmed in some programming language you should always use "else" for site not to show 404 error.
Hope this helps.

[lucy24]

you should always use "else" for site not to show 404 error

A 404 is not an error if the user has requested a page that genuinely doesn't exist. There are worse things than a 404 response.