Referencing and positioning - here is often confusion about the two terms. Referencing means to tell the search engine that your site exists, while positioning is about placing your site as high as possible for relevant search queries.
Very few sites escape the vigilence of search engines, most are therefore referenced. It is quite often the case though that the positioning of a site is disastreous, which is often due to structural problems with the site itself. blue-infinity recently audited a site with perfect design but with a technical architecture that was badly done: only the homepage had been referenced by Google. A Google search on product names of the client didn't even bring up the client's site, but a counterfeight one!
To enhance your positioning on search results, you need to do the following:
- carefully choose your page titles
- add a description of your page in the META tag "description"
- use search-engine friendly URLs (instead of www.company.com/php?id=23 display www.company.com/products.html)
- maintain a consistent navigation
- use descriptive links (not: click here!)
- structure the content of your pages with valid HTML tags
- promote your site and have others link to it.
Read more about SEO strategies in this White Paper on SEO (French)