Frames gained popularity because they made the web masters job easier. Frames rarely enhance the usability of a web site. Large reference documents work well with frames, but most other sites can do without them.

Some search engines cannot crawl framed sites. Text readers for visually impaired people choke on frames too.

Bookmarks or Favorites do not work right. You can only bookmark the top level page of a framed site, not a page you found inside the site. This makes it harder to find the page you want at a later time.

The navigational scheme on a framed site is different. It is different from other framed sites. It is something a person has to learn at your site. Framed sites lose out on leveraging what people already know about navigating a site.

Frames can be removed from a site by adding corporate identity and navigation to each page.

Good web site design will use frames sparingly.