It is important to pay attention to little details that make the site easier to use by visitors. Sometimes small details make the difference, and the user likes our site better than other sites, just because he feels comfortable navigating it, and finds what he wants easily. Of course, it depends on the audience you expect for your website. For instance, if you have a website for professional designers, then you do not need to keep it that simple. Users will find their way and probably enjoy that sophisticated and strange menu system that is a piece of art. But if you expect a general audience, it is better to keep things nice and simple. The site usage should be intuitive. This is a list of several aspects you should consider:
Let the user adjust the font size, avoid using fixed font sizes in your stylesheet. If you use fixed fonts, at least make them big enough so they can be read by people with sight problems.
Make the forms clear and avoid crowded pages. Insert text hints when necessary so users always know what they have to input in each field. You may also use a small help icon next to the form field that users can press to get a pop-up with more...