When is webdesign good webdesign? That's an interesting question, which I will try to give an answer to.
First of all a good website should achieve a usefull goal. The most important aspect of every website is that it does what it's supposed to do.
Second, a website should be easy to use. The user should be able to find the information he needs quickly and efficiently. He shouldn't be distracted by things that aren't important to him. The text should be clear. He must immediately recognise control objects like links and buttons and the pages have to come on to the screen fast.
Furthermore a website should have a nice and suitable appearance. This means that the style of a website should be well adapted to the housestyle of the organisation and the design has to be creative and nice. However this appearance shouldn't compromise the other aspects of quality.
Last but not least the website should work. This may seem evident, but there are still a lot of websites out there that don't work on every browser, ask the user to download plugins, have bad links and more. A designer should know how to make a website look good on every browser and know work arounds for every bug.