Every great website need great content. So you have a great designed website, with great navigation and all, but your visitor do not stay long enough? or not visit your website qite often? The only reason people visit a site is because of the content, dou you have the content needed?
Your website should be dynamic, so visitor will see constant update tha everyone like. Create banners, flash animations to impress their eyes. Put RSS technology in your site for automate content update, or CSS to create a dynamic feeling.