Websites are not for designers and developers, they are for users
Trust yourself and tread your own path
Have the confidence to try your own thing. Don't feel you have to follow the latest trend or en vogue pre-compiler You may be harbouring the next trend in web design yourself, give it chance to escape.
Form follows emotion
Websites are not for designers and developers, they are for users. It is not about the effects, the jQuery or the latest plugin and definitely not how the page adapts as you resize it in your browser ( we all do this don't deny it). It is about improving the users experience and helping them achieve their goals.
People will be more convinced by emotion than by rationale. The human brain is set up to simultaneously process two kinds of information: the emotional and the empirical. But in most people, emotional responses are much stronger than the rational response and usually take over. As a designer you can tap into this emotional response, although well formed markup and the like is really important it is not the be all and end all to a user achieving their aims.
Make and do
Make models, build wireframes and tests along the way. They will help direct you more than a concept alone which has no feeling. The two go together. You hear of people saying you shouldn't use Photoshop any more, of course you should... but you should also make prototypes, wireframes and develop the feel of the thing you are trying to create.
Go above and beyond
Do more than the client asks for. Do what they would like to ask for if they had the courage to do so! The client may want one thing but you should use your experience and knowledge to help nudge them in the right direction, they are paying for your skills as designer/developers which includes telling them if they are wrong.
Can you really design purely in a browser?
Time waits for no one