Allow a Single Variation of Category Pages to be Indexed
Google doesn’t currently have guidelines on indexing different versions of category pages, but is moving towards recommending allowing a single version to be indexed, such as a sort order, and the alternative variations with different filters and sort orders should be noindexed. If there are other specific versions of category pages which are important, you can allow the first page in the set to be indexed as well.
Excessively Flat Site Hierarchy May Confuse Google
An excessively flat site architecture, such as having a very large sitewide navigation or linking to all pages in a paginated set from page 1, may confuse Google about the site hierarchy, which page to rank, and what to show as Sitelinks.
Sites Sharing IP Addresses Isn’t a Problem For Google
It’s common practice for websites to share IP addresses and having an implementation like this won’t cause ranking drops or performance decreases.
Only Use Separate URLs For Similar Products if They Match Separate Specific Queries
It’s usually better to consolidate signals for different product variations by using one URL. You might want to split them out if they match specific user search intents though, as one main product page might be too generic for certain queries.
Splitting or Merging Websites May Change Rankings
If you’re moving a whole website to a different domain, Google can move the signals across for the whole site. But if you’re splitting off part of a site to a new domain, or merging multiple websites, then the rankings may change as Google has to revaluate the sites individually.
Treat Tag Pages Like Any Other Page & Only Noindex Low Quality Ones
John recommends treating tag pages like any other page on your site and to differentiate between useful tag pages and low quality tag pages by noindexing the low quality ones.
When Splitting a Category Page Into Two New Ones, Redirect to One of the New URLs & Update Internal Linking
When splitting a category page into two separate pages, John recommends redirecting the old URL to one of the new pages and then updating internal linking normally within your website’s structure.
Merging Internal or External Pages on One Topic Will Result in Higher Rankings
If separate sites that rank well already and both focus on the same topic or service merge, then they will see an increase in rankings as Google sees an even stronger page than before.
Linking to Every Page From a Site’s Homepage Will Stop Google Understanding Site Architecture
Linking to every page on a site from the homepage means that Google will lose the structure of the website as a whole, unless the site only has a small number of pages.