So you have multiple websites and you link them but is this good practice?
Can I link all the websites I own? *
Linking a handful of websites is okay and may be appropriate, for instance, having site-a that sells ice cream to site-b that sells sweets. This is, obviously, a strong connection so this type of link is okay for Google. But the problem arises whenever you have 50 websites, for example, and you decide to link these sites together. Google does not like these kind of links because one person is unlikely to produce excellent content for 50 different websites.
*Adapted from (GoogleWebMasterHelp 2013: online)
The bigger picture
Since Google has confirmed AuthorRank they will be able to monitor these situations more closely. Before AuthorRank is implemented you are best sorting, if you have a lot of, domains out now. Only link to add to the user experience. One question which will keep you right: If I add link-z will this benefit my user in a direct way?
- GoogleWebMasterHelp. (2013) Does linking my two sites together violate the quality guidelines? [Online] [Accessed on 25th April 2013] http://www.youtube.com/watch?v=x0-jw_PfwtY