How do sub domains affect SEO? Please share your thoughts..

Thanks

I don't think it affects seo as long you have a good marketing campaign. You can promote a sub-domain the same way as a regular domain name.

The domain name is only part of the formula used to rank a PAGE.

It is NOT about the domain name but the CONTENT on a PAGE, that is the main factor. All other factors' relevancy to the PAGE content are added bonuses.

If there were two websites, each with near identical keyword saturation, near identical content, near identical meta tags / titles and URLs:

1) no-keyword-domain.com/vehicle-reliability.php
2) audi.no-keyword-domain.com/vehicle-reliability.php

and if the content on those two pages were about the Audi brand of cars, it is possible that website number two could rank higher than website number one because of having Audi in the domain name for a search relating to Audi vehicle reliability.

There may be NO advantage to either web page for the following structure:

1) no-keyword-domain.com/vehicle-reliability/audi.php
2) audi.no-keyword-domain.com/vehicle-reliability.php

if the search phrase was are Audis reliable?

But website two could have an advantage if the search term was Audi vehicle reliability reviews

Factors used in my example are only a portion of what the search engines consider important - the Google, for example, uses over 200 factors in determining where to rank a PAGE...