Web Hosting :: Tips On Using SubDomain

Points to consider before using subdomains

Subdomain makes the URLs shorter and nicer. It allows website owners to categorize the
content of the website. It also
helps in improving the search engine rankings as most of the search engines treat
the subdomain as a separate website address. However, there are certain things to
consider before setting up subdomains for your website.

1. packages. If you have subdomain and want to move your site, you have to
   choose one which supports subdomains.


2. Most web hosts charge extra for subdomain setup and maintenance.


3. If you use cookies in your website, a cookie set from a subdomain
   cannot be read from the main domain and vice versa because of the security
   association feature tied to the domain which set it. This is also true for
   session cookies, where, if the user is logged in on the main site, and
   then moves to a subdomain, the subdomain site will not be able to access the
   same session cookie, and will assign a new session (hence forcing the user
   to login again). However, session persistence
   across subdomains can be maintained by implementing URL rewriting instead
   of session cookies.


4. Your website stats will often not include the statistics of the
   subdomains. Therefore, you have to setup separate statistics for your subdomains.


5. One of the advantages of using subdomain is that the website can be broken down into
   smaller pieces without losing the brand image associated with the domain name. The subdomains can be hosted on
   separate servers in order to reduce the burden on the main domain hosting server.

Sharing cookies among all subdomains

As explained earlier, cookies are not shared among subdomains or between the domain
and the subdomain. In order to set cookies accessible by all subdomains, use the
following techniques:

1. While writing the cookie, set the cookie domain to ".domain.ext" so that it applies
   to all subdomains.


2. If the cookie domain is set to ".domain.ext", it will not be accessible by a user
   who types in the address without the www before the domain (i.e. http://domain.ext).
   Therefore, redirect all requests without www to http://www.domain.ext.

There are some reported problems with the above approach. It is safe to set the default cookie
with no domain specified and then set another one with domain as ".domain.ext". In this case
there is no need for the redirects.
However, remember that session cookies are set by the web server software and you may not
have control over how the cookie domain is set.