I want to have all these linking to the one page" www.mysite.com/articles www.articles.mysite.com articles.mysite.com Is that a problem? or is it better to have just one of those? Becuase I can't seem to work out how implement articles.mysite.com while stopping mysite.com/articles from working Thanks
You will not get benefit of creating multiple URLs . Better Create one and concentrate on building quality backlinks.
It's a very bad idea, it's what known as a canonical url issue - the canonical url being the one that you want to be used. You should permanently redirect to one url
Its definitely not good idea to implement such URLs it will effect negatively. For implementing article section in your site you can take help of Blogging software such as wordpress. Moreover it will provide you SEO plugins also through you can also utilize your article in favor of site.
As madga said, doing that is creating URL canonicalization issues. You never want multiple URLs being used to display the same content. You end up with duplicate content issues and split PageRank/link juice... both of which can adversely affect your rankings. You'll want to pick ONE of those as the home for your articles, and 301 redirect web page requests for the other versions to the one you chose.
As already said by Canonical this will raise a problem named after him ( or probably he is named after the problem ) In simple words, when google finds same content at multiple location it treats the first one encountered as original and others as duplicate, but selecting the original and the duplicates is not so simple for google. It may or may not index the duplicate pages. It generally penalize duplicate content with low SERPs. I can not understand why you can not avoid the content to exist at www.website.com/article when you put it in articles.website.com ? 301 redirection is always the solution.