Website redesign for usability is really an abstract concept. It means to take an existing website and make modifications to is so that it is easier to use.
In some cases it means removing things so as to help streamline it. In other cases, it might mean adding items to help explain different items as well as to improve the flow of the site.
The first step in website redesign for usability is to determine what the issues with the site are. This could be in any of the following categories: