Successful sites require more than just an attention to graphical detail. Just because you've got great photography, or icons, or illustrations doesn't mean your site will be a success. Effective web design is the ability to effectively communicate your message to your client. Effectively creating an interactive experience with your user. And effectively achieving your goals through the combinations of all of these elements.
As important as the attention to detail executed on a site’s exterior – is the skillful execution of valid markup. Well what the heck is valid markup? Its the difference between good code and bad code. In a nutshell. The web standards movement is a movement to try to bring consistency to the way sites on the web are coded, and the way browser's read that code. Therefore coding with standards in mind can save you headaches down the road as the web continues to evolve. It also makes your site more flexible for the next developer that comes along, as he can seamlessly pick up where the last guy left off.
Search Engine Optimization helps your target audience find your site – what strategy is more important than that? SEO is an oft neglected detail of many a sites development. Think of it like building a town, but forgetting to put in the roads and signage for people to find you – and get there. SEO is not so much a set in stone technique, or science, but a constantly evolving strategy. It is organic. It's not something you can just put into place and forget about, because being ranked number one today, doesn't mean you'll be number one tomorrow. But don't let that scare you, a solid SEO foundation, will help you stake your claim on the web. And there are numerous strategies to help you build upon it.