An excellent Web site is of little benefit if it's existence is unknown. It is necessary to be very proactive in promoting the site.
At minimum, the site has to be submitted to the major Web search engines. In addition, the technical internals of the pages have to be structured in a way that takes account of the widely-varying methods used by different search engines to index the pages.
The site must also be promoted by announcements in appropriate forums and vertical-market listings.
Where possible, links from other sites should be cultivated. This can have a marked impact on the exposure of the site.
I can undertake all the generic activity on your behalf.
I can help you to develop promotion methods that are tailored to your specific operation.
Your own or your advertising agency's basic skills of overall design and copy writing still apply to the Web.
However, it must be emphasised that the Web is a medium in which most of the old rules do not apply.