A site or administrator will often request the services of a search engine optimization company, SEO firm or SEO provider to provide them with SEO services. An SEO consultant with an SEO company works on behalf of a site or network of sites to provide advanced SEO services. These services can often prove to be essential to many internet marketing campaigns. SEO firms, companies and providers will often include search engine optimization as part of a multi-pronged marketing campaign. SEO services are highly valued (because of their high effectiveness) by sites and administrators and therefore are rarely offered by SEO providers as part of a package. SEO services must often be negotiated as a service separately from the rest of the marketing plan. The knowledge and know how to employ advanced SEO services have provided a market for SEO companies to exist and keep them in demand.