Successful, profitable websites include the following considerations
For most of the commercial business web sites I manage, the fundamental aspects of design and successful implementation are:
Content: The text and wording on the site should be relevant and topical to the site and should target the demographic and market your business most frequently caters for.
Usability: Your business web site should be very user-friendly and easy to understand what to click on and how to find detailed information using a menu or navigation system that conforms to the usual defacto standards reasonably well. I'd usually be using either top horizontal or left vertical menus work best.
Appearance: The look of your website is important but it can also be quite minimalist if you absolutely hone in on your market. I prefer to build websites where the site framework is complimentary to the information and is subtle in it's styling so that you don't notice any one particular aspect of the site but get an overall feel for the quality and tightness of the web site.
The graphics and text should be styled in a consistent way that flows throughout your website systematically. Ideally I like to be able to design the content as well as the website. The style should be professional, appealing and relevant and appropriately themed.
Search Engine Optimisation: Your site must be easy to find via all the major search engines. I typically use Google.com.au as our benchmark because if a website is found in there under the key phrases we are targeting then the other search engines tend to produce similar results and we find most people do use google for search. Some of my recent successful search engine marketing results for clients you can read about in my blog under "Search Engine Optimisation (SEO) Success Stories".
Statistics: The website statistics package that comes with every website I host is very detailed and shows aspects such as what keywords people are searching with to find your site, what pages they are visiting, how long they are there, what are the most common sequences of page view and how many ‘hits’ (page views, unique visitors etc) did you get.