What makes a website redesign successful to me is not so much changing the site. It,sometimes is a matter of whether the site needs more or less. Sometimes less is more. A lot of websites have so much going on that it becomes distracting and unappealing to the audience. I feel like redesigning a site like this could help it. You could subtract some images or text or a column to make it more attractive. Sometimes it depends on the particular company, client, or organization.Some sites may atrract a more gaudy, accentric crowd. Some sites may attract a more corporate and conservative crow. Redesigning a site could make or break it.