I am trying to summarize elements of a good web application and web site design. This question was asked earlier in various forms and my intent is get some must haves, good practices and definitely avoid kind of items.
I have come across a good document from adaptive path on Patterns for Signup and Rampup and I like it.
Welcome all input and references.
In general, I believe, a "good" design is one that supports the purpose of the web site. Thus, there's no general answer. It simply depends on the purpose.
However, there are some elements that every web page has or should have in one form or another:
Call To Action The most importent element. You want your users to do something, so you must tell them what to do. What it is depends on your web site or product. There may be several calls-to-action, and a series of them is often called a (sales) funnel.
In general, the less steps necessary to complete an action, the better.
Interactive elements Everything that enables the visitor to do something: Forms, buttons and other widgets. Their purpose should be obvious.
Copy This is used to describe the benefit or utility of the product, establish a certain emotional mood, provide information about your product, and -- most importantly -- answer ANY objection visitors may have NOT to act on the call-of-action.
The most common objection is risk-awareness or uncertainty: Will following the call-to-action really provide the promised benefit? Typical solutions include guarantees, testimonials, free trials, etc.
Headlines There are basically two camps with different ideas what headlines should do. The first ones assumes the purpose of headlines is to describe the product and/or its main selling point. The second camp assumes their purpose is to make the visitor read the first sentence of the copy. These are not mutually exclusive, so one may find a headline which does both, sort of.
Depending on the camp, sub-headlines are then either used to structure the copy or to provide additional entry points to read the copy, respectively.
Graphic design Often over-emphasized, but sometimes useful. It includes logos, CSS design, images and video. Graphics is good to improve recall or recognition, to establish an emotional mood or atmosphere, and to add credibility.
Sometimes, it's also used to suggest additional benefits that are either hard to describe in the copy, or that you don't want to describe, at all. (Think, for example, the fetching girl in a car ad).
Graphic is also relevant when leading the visitor's attention, thus graphics should emphasize the important elements, usually the calls-to-action and the headlines.
On top of my head, that's it. Basically.
Hope this helps.
A good website and a pretty website are 2 completely different things. I am going to assume want to talk about a good website because ultimately looks aren't the deciding factor when someone uses a website (craigslist for example).
KISS principle - Keep it simple stupid. I live by that.
If you make me think about how to do something, you have failed in producing a good user experience. I should just know where to find things the first time I use your site without you having to give me a tutorial. You must also provide me the shortest amount of steps to complete a task. The fewer amount of clicks I need to finish a task the better.
Also, don't bombard me with tonnes of information at the same time. I am not going to look at 98% of that information. A good example to WAY to much information is the NYTimes website - http://www.nytimes.com/. It scares the user because they don't know what to do next. Don't provide to many options, tell them you want to do A, B or C and not A - Z. The more options you give the user the more you reduce each options (as Claus said) "call to action". They might even end up leaving.