It is necessary
The programmer is specialized in basic site structure such as PHP or ASP and databases as well as HTML skills
As for the designer needs different skills such as dealing Alfotoshob or any image processing program such as Firework and learn to design Flash animation animation and learning the design of pages in a program such as Dreamweaver or Frontpage or Microsoft Expression in addition to the skills dealing with CSS and JavaScript language
Often the designer and developer is the same person who is understood in both sides and has a technical taste
The programmer is specialized in basic site structure such as PHP or ASP and databases as well as HTML skills
As for the designer needs different skills such as dealing Alfotoshob or any image processing program such as Firework and learn to design Flash animation animation and learning the design of pages in a program such as Dreamweaver or Frontpage or Microsoft Expression in addition to the skills dealing with CSS and JavaScript language
Often the designer and developer is the same person who is understood in both sides and has a technical taste