"Success is the sum of details." - Harvey S. Firestone
For some it's the last thing you think of, for some it's the first. No matter how you as a person deals with details you're generally aware of their importance. This applies just as much to web design as it does to print design, interior design and life. While broad strokes will get the information across, the small details can turn a visit into an experience. When the details have been considered and taken care of, it reflects well upon your design and the client you're designing for.
When I talk details I'm talking navigation, buttons, link colors, and the small bits of typography that sometimes get thrown together last minute. These are the bits that are often considered quickly at the end, but including them in the beginning and as part of the process can make it a much more natural integration.
For smaller websites this can make even more of an impact. Without extensive navigation and lengthy content you can make your user's experience a memorable one by rounding it out with little touches and getting playful (without sacrificing accessibility of course).