Portal websites
Portal websites can be submitted to the search engines just like your main site. What this means is that the more portals you have, the more visitors you will get. If your website is doing alright in the search engines, then imagine having five more websites out there for the spiders to find. Five more listings mean that Web surfers have five times as many ways to find your network of websites. You still with me? Portal websites are just like sub-domains but they do not have their own URLs, so it is actually cheaper than subdomains.
Search engines and links go hand in hand. More and more search engine spiders or robots are taking into consideration the number and ranking of sites that are linked to you. By linking your sub-domains to your main site and to each other, the ranking of all of your sites is going to be greatly improved.
