Ok, so you have decided you need a web site - but have you thought about what it will actually do for your business? The obvious answer is that it will advertise your business - but how will it do that?
Just having a web site isn't enough these days - it needs to be part of a marketing plan, so that you put the necessary activities in place to bring people to your site. You may think that simply setting up a site means that people will find it through Google, Yahoo or MSN, and ten years ago that might have been the case, but these days the web is such a busy place, unless you have a very unusual product or service, your web site will be lost amongst thousands of others word-wide all competing for attention. This is where SEO can make a huge difference. In order for you site to be displayed near the top (or at the top!) of the list when someone searches for a phrase using Google (or another search engine), your site needs to be optimised so Google can rank it against other sites.
Some web designers will still try to blind you with science talking about Meta Tags and suchlike.
This is, to a certain extent, old hat - the main search engines such as Google stopped placing any importance on these several years ago, and now use a strategy of rating the "importance" of your site by the number of links to it from other sites - and those other sites also need to be rated as "important", by having lots of links pointing at them.
Search Engine Optimisation (SEO) - An Introduction