The Sub-pages on your Website are often completely neglected as part of a strategy to promote a web-based enterprise.
Website proprietors are inclined to spend most of their time seeking to advance the PR worth of their home page and to get backlinks to this page and otherwise work on its SEO. But if you think about what's involved, and what you are trying to do for a moment, you will realise how difficult, frustrating and fruitless this can become. Remember that Google and other search engines index PAGES not WEBSITES, and so each of your subpages can have its own exclusive persona and can become a unique and profitable niche market right on your own website.
With your HOME page you can only really focus on about five keywords and one or two keyword phrases. You may spend hours and hours carefully editing your metatags and page content to maximise the effectiveness of your selected keywords words. BUT the phrases and keywords you select have to be general phrasesrather than specific ones. It is your home page after all.
For example for a travel site the information may have to be about a Country or a region, rather than a specific town or city. Your competition in this general area will be HUGE and well established with thousands of backlinks already in place. To complete you will have to build more backlinks than them and get equivalent PR for your home page.You have set yourself an unrealistic task that may take years of work.
Also it is worth considering what most persons are looking for when they conduct a search. Let's use an example. Say you are evolving a website promoting holiday rental places to stay in Spain, and your have built your contents focused on the keywords: 'vacation', 'rental', 'holiday', 'accommodation', 'fun', 'Spain'. Most people who are looking for a vacation in Spain will search for an exact location where they want to take a holiday - for example 'Barcelona', or 'Madrid'. They will probably not use the word 'Spain' in their search phrase. They may furthermore exactly specify the type of places to stay they are looking for e.g. 'Vacation apartment for lease in Barcelona'. They will be very unlikely to find your home page with these search terms despite all your hard work.
The trick is to work on your sub-pages and get them out fishing for customers for you. Having 5 or 10 rods, lines and bait in the water is much better than one!
Google and all the other major search engines will use your site map and will index all of them if you work on the SEO and you regard them as niche market sites. The sub-pages have their own persona and are returned individually and specifically in the search results.
You could create a sub-page expressly for 'Vacation rental in Barcelona' and this would save you the expense of having to purchase a exact domain title for that page. Of course the PR ranking of a sub-page will never be as high as that for your home page, but it can be very close, and with a bit of effort you can add literally thousands of sub-pages each with their own set of expressly targeted key words for a niche market.
All these pages will be out there angling for clients and angling for natural backlinks for your home site as well. Sure it will take many hours of work to create all these individual sub-pages and boost their SEO and to get Google an dthe other search engines to index all the pages, but it will be worth it. This involves making certain that your metatags and page contents are not replicates and getting deep backlinks for each of the individual sub-pages. But the costs will be much lower that buying domain titles for all the thousands of pages you may want desire to develop. You will find that there is much lower competition, and generally lower PR values for the specific niche page, and PR values of 1, 2 or 3 will usually get you on the first page of results for the search terms.
You can even select your title for the page to closely align with your keywords, for example 'rentinbarcelona'. This URL would have long gone as a choice for a full domain name! BUT you can use it as the URL for your sub-page - 'mysite.com/rentinbarcelona.html' - with the Title " Rent in Barcelona - Quality, Affordable Holiday Accommodation'.
Your should avoid the pitfalls of a sites using databases and PHP to deliver the sub-pages for your website. The problem is that Google won't index these details for sites that are delivered dynamically and will only index your home page. This is what your competition has done - DO something different - build a specific sub-page for hundreds of niche markets on you website - that will be indexed by Google. This is what the customers want - focused search results on specific niches.
One site that does this is shown below - it has more than 2000 pages, all indexed by Google, all micro niches, all out there fishing. Heaps of Work - But it Works!