If in doubt, keep it simple. While some people might like the purple-on-orange combination, it certainly won’t be to everyone’s tastes.
Make sure your site works. I’ve seen plenty of websites that don’t work in my browser of choice (FireFox).
Don’t overdesign your website
The royal “we” Be honest with your clients. If you’re a sole web developer, don’t tell them otherwise
Stock imagery clichés (clouds, fish, sapling metaphors, …)
Dodgy portfoliosA good portfolio needs to consist of as many decent, working, live sites as possible. Quantity is also important in a good portfolio – one or two sites given implies a lack of experience. Any more than 10 examples are probably wasted, but a good number of quality sites will help to increase your visibility. Don’t feel tempted to include lower quality sites in your portfolio just to bulk out the numbers, though – one bad site can cheapen the rest.
Over-use of technical terms
.:: Stuart Brown
Flash intros