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If you merge the two sites say into atlantaeventscorporate.com and 301 all of atlantaeventweddings.com content to its new location at atlantaeventscorporate.com you will effectively be combining the page ranks and traffic scores of the two. Of course its not quite that simple and there are ways this could go wrong but I would look into that. Perhaps just turn wedding into a subdomain with a directory style url?

I'm tempted to say in order to optimize local search results I'd go with:

• www.website.com/city1/stop-smoking

• www.website.com/city1/weight-loss

etc..

you would need to edit the single.php file.
look for:
<span < code="">class="post_date">`'j F,Y'); ?>`

change it to:
<span < code="">class="post_date date updated">`'j F,Y'); ?> then for author look for:</span <>``</span <>`

```<span < code="">class``=``"theauthor"``></span <>``or<span < code="">class``=``"theauthor"``></span <>``change to: <span < code="">class``=``"vcard author"``>
<span < code="">class``=``"fn"``>`

or
<span < code="">class="fn"``></span <></span <>`</span <>````` 
preferably you would copy the existing parent themes single.php file into a child theme and make the edit there

/e I should mention that it is common for theme creators to abstract out these functions into less comprehensible formats like this entry from the Avada theme:
| Personally either way I dont bother to fix these particular "errors". But that is mostly because authorship markup ranks nil in regard to what I am up to.

Your other option is to delete or comment out the existing related markup and write new or utilize one of many plugins that will address this particular issue.````

Yes you can remove the original Ga code in exchange for the tag manager container code and it will handle the rest.

Your goals will not be affected as long as you have your firing rules correct in tag manager.

Highly recommend the Chrome Extension Google Tag Assistant to make sure you get things the way you would like.

Id probably go this route for a simple solve. I believe you would want to remove or disable the current handicapped markup.

I'm not sure I just know from experience. The first tag I create when I make a container for a new site:
Name: Page Views
Tag Type: Universal Analytics

Then i set the tracking id there.
It gets the all pages firing rule and then since I use WP for a platform I also create blocking rules to eliminate admin and login views.

/e I should be more clear and say that it does not replace but the two tags will both be present it's just that the tag manager code snippet you maybe pasted right over the old analytics one now inserts any required analytics code for you.