… have a good design sense and understand the fundamentals / design principals.

… know all the major design software including the entire Adobe Creative Suite.

… have some basic video editing skills.

… know HTML, CSS, and JavaScript.

… know enough about server-side languages (PHP, ASP, Ruby, Python, etc) to understand how they work, what they do, and the possibilities of their use.

… know about servers, hosting, domain registrants, DNS, etc. Setting it up, and fixing it when it breaks.

… know OS X really well (and enough Windows to get by) or know Windows really well (and enough OS X to get by) and know a huge variety of utility software that goes with.

… are good photographers.

… can color correct photos and work in RAW.

… can cut clipping paths or otherwise extract objects from photos.

… have a killer online portfolio.

… are a personable, nice people that are good with clients.

… can help clients with anything even vaguely computer-related.

… are quick to adapt to new software and new technologies.

… can train fellow employees.

… can train clients on the use of their websites.

… are good communicators.

… are team players.

… have good taste in art, music and movies.

… are up to date on social media.

… are good at logic and deduction.

… are good at user experience and user testing.

… are SEO experts.

… know about and how to handle web accessibility (and the laws surrounding it)

… understand copyright laws.

… do progressive enhancement and graceful degradation techniques.

… can debug cross-browser problems and older browser bugs.

… can bring your own client base.

… are healthy, well groomed, and wear fancy t-shirts.

… can be on-call at all times for emergencies.

… have college degrees in design-related fields.

… own very nice and expensive computers full of expensive software.

… can design for mobile devices.

… are good typographers.

from CSS-Tricks