This varies and is actually slightly less for AOL and WebTV users. Statistically speaking, frames are annoying and rob viewers of usable space. This is not to say that frames cannot be used, but they should be used sparingly and usually only on sites that could benefit from frames as navigational tools or in special design implementations.
Navigation is perhaps the most important layout item on a site.
Main content or information should be accessible from anywhere in your site in 3 clicks or less. This can be tricky in large sites. Design Bandwidth is critical. A site with long load times will cause a viewer to leave in a hurry. The number and size of your images.