Keep your site downwardly compatible to Netscape 2.0 and Explore 2.0. The drawbacks of frames far outweigh the benefits of frames. My opinion - frames complicate the Web browsing experience. Read To Frame or Not to Frame for more advice. Drawbacks of Frames Back button does always work.
Visitor looses track of which frame they are currently in.
Content must often be crammed in to fit inside a frame. Benefits of Frames Visitor doesn't have to scroll as much More content can be packed into a single page. This technique is usually done for ad exposure. When visitors click on a hyperlinks they don't want to be subjected to a new browser opening up on their desktop. Visitors feel a loss of control when new browser windows start popping up.