milosevic - 9:50 am on Nov 12, 2010 (gmt 0)
To create web designs you don't need to know any of those things. These are things needed for developing websites not designing them... assuming that the OP isn't confusing the two.
Web design is used too much as an umbrella term, web design should be for the visual design only, and web development should mean the coding of that into a functioning site.
There are people out there that design websites and don't know any HTML - I too have done jobs for someone like this in the past.
However I think that with the emergence of CSS3, Photoshop design for websites is becoming increasingly inefficient compared to creating styles with CSS.
For a commercial website other things need to be taken into account during the design stage, such as information hierarchy, usability and SEO - some would say that this is the real important part of website design, at least for commercial success.