(updated 5/20/99) The basic purpose of framesets is to subdivide the browser window. This way, only part of the window scrolls or gets replaced as a user navigates through a Web site's pages.
Web builders often use framesets for toolbars, where one frame holds a static menu page and users click items in the menu to change the content in another frame. This approach can reduce overall file size because the menu page doesn't have to be included as part of each content page.
The trade-off for smaller files is increased complexity. Frames add another level of site management, since hyperlinks must not only point to the appropriate pages but also load into the appropriate frames.
Another problem with frames is that most browsers can bookmark only the initial contents of a frameset. No matter how deep into the frameset users are when they set the bookmark, using the bookmark returns the browser to the initial pages of the frameset. This limitation makes it very difficult for readers to return to specific content.
However, if your site's information is well-organized, with navigation only a few levels deep, frames may serve your audience well. Users may appreciate the easier navigation, even if they have to click through the opening page each time they visit your site.