When designing a webpage one of the goals is to allow the user to focus completely on what they are looking for. You do not want the user to get confused by the navigation of your site, not understanding where buttons lead or how to get back to what they were looking at before.
When a site has been designed well and has a well functioning flow the user will not even notice the design of the website because they will be too focused on the information that drove them to the site in the first place. Take for example learning to ride a bicycle. When a child first learns to ride a bike all of their concentration is on the bicycle. They are focusing on the handles, the brakes and the peddles, they are not looking around noticing the birds singing or the wind blowing in the trees. Once the child has mastered the skills necessary to ride a bike they no longer pay as much attention to the bike itself, instead they are having fun going as quickly as they can and racing their friends. This is the concept of the flow of your web design.
You want the flow of your website to be natural and easy. If the user notices the flow of the website then more than likely they have been distracted from their purpose for being on the site. Sites need to be designed with the user in mind. Why is the user here? What are they looking for? What types of things is the user going to need to do while on this site? There are a number of things to consider.
