Designing good websites is not simply a case of throwing a load of funky graphics at the screen, there are 3 main areas to consider, here I give a brief overview of these key areas and explain why they are so important.

Content
The whole point of the majority of websites is to provide content, be it text, pictures, mp3s or videos to users. When you build a site the first thing you should consider is the content. How much is there likely to be, how often will it change, what content do you want the visitor drawn to first and so on. Design the site to fit the content, don't create a site first and then try to decide where to put everything, it simply wont work. Additionally content needs to be kept fresh and up to date at all times. You will never get repeat visitors if your content doesnt change, however impressive your site may look.

Accessibility
There is no point in content if people cant access it. Furthermore you do not want to limit accessibility to those people fortunate enough to have the latest browsers & plugins, with high speed connections and with no special requirements. The World Wide Web Consortium(W3C) publish guidelines to aid developers in creating standards compliant websites by writing clean, browser-friendly code. They also provide automated services for checking that your web pages conform. It is important to note however that compliance with these guidelines does not automatically ensure your site is fully accessible to all potential users. The best way to achieve this is to test your site against the Web Accessibility Initiatives guidelines. These are purely self-tested and if you decide your site has passed you can award it with an A, AA or AAA logo.

Presentation
Presentation has very close connections to certain areas of the accessibility issue. In particular good use of colours is important from both viewpoints. Too many colours makes any site look un-coordinated and messy. Stick to a few basic colours for text, backgrounds, logos etc and use different shades of those colours to add depth. Make sure text colour and background colour are significantly different to make reading the text nice and easy. Similarly do not use an array of different fonts, stick to one or two throughout the site. Serif fonts such as Impact are good for, surprisingly, making an impact on a visitor whereas sans serif fonts like verdana are much easier on the eye when reading. Large blocks of text look very unwelcoming to visitors so try to avoid them particularly on the homepage, break text into paragaphs and sections with sub-headers, lists and so forth, use images where appropriate to give the user a break from reading.

Overview
It is important to note that all three of these components are vital in creating good sites but the balance between the three will vary from site to site. Just remember: Plan the design to fit the content; keep content fresh and accessible; make the site pleasing to look at and interact with.