Frames

Frames are a much disputed topic. They segment the page so that part of the layout remains fixed on the page (often the menu ) whilst another section changes.

See http://www.phys.unsw.edu.au/photogallery1/ where thumbnails are in the navigation frame and larger blow-ups appear in the main target frame.

Frames sites are harder for search engines to index, can't be bookmarked beyond the top level URL and are not supported by old browsers. They have however been used to good effect by many designers.