Forum Moderators: martinibuster
It is better to create a different directory within your main domain for such content ie in your example, www.yourmaindomain.com/blue.widgets rather than having www.yourmaindomain.com and www.blue.widgets.com
The reason is you can safely link to your hearts content within a single domain. If you wanted you could crosslink all the pages in the www.yourmaindomain.com/blue.widgets directory with all the pages anywhere else in your site and you would not get penalised for crosslinking.
But if you crosslinked all the pages on www.yourmaindomain.com and www.blue.widgets.com you are leaving yourself open to a Google crosslinking penalty.
But a quick summary - crosslinking would be if I had a number of domains and linked them all together. Google frowns upon this as the whole idea of linking is that each backlink (or incoming link) is viewed as a 'vote' for your site. So if all the 'votes' were not from independent sites that liked your site but were in fact from other sites you owned, that would be considered cheating.
EG say I have a dozen domains called mydomain-1.com right thru to my domain-12.com
On mydomain-1.com I link to mydomain-2.com, mydomain-3.com, mydomain-4.com etc (ie to all my other domains).
Then I do the same with all the other 11 domains, linking to the home page of each of the other 11 domains (in effect making one big circle of linking amongst my 12 domains).
That is crosslinking and not allowed (although a lot of unscrupulous webmasters run the risk as it undeniably boosts your PR and position in the SERPs).
But there is no such penalty for a 'circle' of internal pages linked together (crosslinking) within a single domain, you still get the aforementioned PR boost and Google is fine with it.
For your specific case, as long as you don't crosslink your secondary domains to each other you can still safely link them to your main domain.
IE: www.yourmaindomain.com can have reciprocal links with blue.widgets.com, guide-red.widgets.com and all your other domains. But you CANNOT then link guide-red.widgets.com to blue.widgets.com and your other secondary domains otherwise you are running into crosslinking territory.
You should be okay if you:
1) Exercise restraint. No one knows how much is too much, but don't go overboard and put links to every page on every other page. Link selectively, and focus on relevance from the user's point of view.
2) Cultivate outside links. Invest some effort to develop quality external links for the sub-sites as well as the main site, so that your own interlinking is not their only source of Page Rank.
I have a main domain selling a widget program. Every buyer of the widget program is a sub-domain with a link back to the main domain. But none of the sub-domains link to each other.
Is that OK or is the widget program design going to affect the ranking of the main domain?