Successful Web Site Development requires knowledge and skills in many areas, and constant attention to six processes.
I also think that the World Wide Web is a unique medium, and that a Web developer should take advantage of--and work with--its qualities and characteristics.

Six processes:
Developing information for the Web requires a focus on meeting user needs. To accomplish this, our methodology involves six elements and these six continuously ongoing processes:

Planning: define target audience, purpose, objectives, and policies for information development and use.

Analysis: check technical construction of web with validation tools; evaluate information consistency and verify correctness of domain information.

Design: separate information into page-sized chunks; connect pages along routes of use and user thinking; provide information, context, and navigation cues; create a consistent look and feel.

Implementation: create an extendible directory and file structure; use HTML tools where helpful; use templates for supporting consistent look and feel; check implementation in various browsers.

Promotion: target publicity releases for general Web audiences, potential users, and current users; follow online community norms and practices; innovatively connect with users to meet their needs.

Innovation: continuously and creatively work for improvement to meet user needs; use testing, evaluation, and focus groups to shift and change web's content as user needs change.