What constitutes good web design?

That is the question that I am asking myself and having trouble answering. Is it the combination of layout, colours and fonts used? Or is it something rooted deeper like the navigation structure, usability and accessibility issues or availability of information?

I have come across some really good websites when trawling the internet, but at the same time some really aweful ones. Take Amazon for example, I once thought that it was an ideal way to represent the products that they had available, however it has changed little over the years and I now find websites such as Play and Extremepie favoured in the design aspects. It could be argued that they have been designed with a target audience profile that fits my picture (which is maybe why I like them).