Speed of movement is enhanced by repeating basic formats. If a page includes a background GIF file, for example, speed is enhanced by using such a handful of different backgrounds for major sections. Once the GIF is loaded, it takes little time for it to do its job on each succeeding page, but if the backgrounds keep changing, each change will require new loadings, thereby slowing access speed. The same is true for small logs and banners. If repeated, they do little damage to efficiency.
Random variation is the enemy of glide.
It is also a violation of good esthetics. Provide visitors with enough information to make wise choices. A list should fully encompass the major categories of the material being offered with labels which clearly indicate the kinds of information which are contained at each of the next levels. Provide navigational tools in a systematically consistent fashion. It is all too easy to get lost unless the visitor can always count on finding certain buttons on every page located in the same spots.