As a web developer I translate a graphic design file into a web site any browser can show you.
If you have a large site you might pass on my work to other people who attach it to the databases that make it interactive.
Most smaller websites don't need this complexity. Like this site they function beautifully and connect your users with your business.
If you are a professional here is a summary of what I can offer your company:
Creating structural, semantic markup, as most standardistas recommend, still takes time, thought, and hand-coding.—Casper Voogt, web designer