For the User
You are not my client. Yes you may have paid a pretty sum for your lovely custom designed website, and been assured that it follows all the rules and guidelines for successful coding and SEO. However - if the site is as you think it should look and operates in the manner that has been recommended by you, then the reality is that you're not making the best of your online presence.
The most successful websites on the planet, the Amazons, Paypals and Googles actually aren't as pretty or advanced in operability as you might imagine, because the creators have taken into account the average user. Users of websites are the actual clients of the experienced website developer. Without the users of your website you would have no business, so why not ensure that your website is as easy as possible for them to use?
Content is king
It's an old rule, but it's the truth. It used to be said that any piece of important content on your website should be no more than 3 clicks away from the landing page, otherwise users, (your customers), will go away and try somewhere else. This piece of advice still holds true today, where virtually every business has several competitors
Optimise for the User
Website development and design is more than just putting your information online, surrounded by pretty colours and slapping on some means of payment. Without carefully considered, optimally built databases and supporting server code, and standards compliant, search-engine friendly markup, your information will never be found, let alone seen by the those who are the real clients, your customers - the web users who are actually make those online payments.
The best web development takes into consideration the optimal paths to success at all levels, from designing a database for both speed and ease of access to the data; via optimised, rational server code to handle requests; to genuinely user-friendly online markup and interactive functionality that not only makes your services easy to find, but pleasurable to browse and purchase.