I want to know about a issue. If i have a website like domainname.com and if i make some sub-domains like xxxxx.domainname.com and putting such sub-domains on index page of my website then are they considered as outbound links just like other outbound links.
Yes they are. Subdomains are considered by search engines to be separate domains for their purposes. The best way to use a subdomain is to create an independent site that is part of a larger network of "sub-sites" such as how CNN.com is organized (you have the main site, then you have children sites such as "Money" and "Sports" - Yahoo.com does the same thing). You can also use subdomains to separate services that a site would offer (such as putting the mail server on a subdomain).