How much does "Sud-domain SEO optimisation" improves website ranking?

[vtmoz]

Let's say there is a website(domain) and couple of sub-domains (around 6). If we optimise all sub-domains with "keyword" we want our website to rank for.....like giving "keyword" across all page titles of sub-domains and possible places which looks natural as brand mentions. Will this scenario helps website to rank better for same "keyword"?

How can these sub-domains do really influence website in rankings? Like if the sub-domains have broken links, will this affect website SEO efforts?

[Andy.Drinkwater]

Hi,

I wouldn't be using sub domains in this manner to try and influence the main site.

I would be concentrating heavily on the primary site - write amazing content on there, share it, try some link acquisition, optimise the pages for keywords carefully and look at how useful what you are creating is going to be for your visitors.

Don't ignore usability either - make the site easy to navigate and create a pleasing experience for your visitors.

-Andy

[vtmoz]

The actual reason why we opted for this idea is the way our website and sub-domains built. We have nearly 10 sub-domains with thousands of pages. These are killing us not to rank better with several issues like broken links, internal redirects, link juice dilution, etc. We cannot really control all the pages in sub-domains as they all have thousands of visits. So, I am thinking the other ways to influence the website rankings with same sub-domains. Can you please tell me how this gonna work. As I told in my earlier post, I will make sure this optimisation will look natural to the possible and doesn't affect usability. Finally, I would like to know what's the impact of bad sub-domains on website if they are not well optimised?