If you don't have that department's support from the start, it will not share responsibility for what was developed. In fact, it may become adversarial, simply because it was left out of the process. Oversights made by failing to get everyone's buy-in may also require costly repairs after launch. So keep your peers in other departments well-informed and a part of the approval process. Acknowledge that Web sites are never finished.
Web sites are high-maintenance creations.
Keep a core staff available to continue development and repairs long after launch. Assign a dedicated team of programmers and graphic designers to keep the site going and to ensure that your department is responsive to change requests. Do your development using Windows machines, not Macintoshes. Whatever your personal preference, Windows machines are still the lowest common denominator when it comes to operating system features. They also happen to account for at least 90 percent of the installed user base.