Most current sites use a two-frame format.
When frames were first introduced, they were received with great enthusiasm. So positive was the response that frames were often abused and became subject to much derision by many in the Web community. In particular, sites would become so heavily framed that it actually hindered easy navigation rather than assisted it. As with any other Web authoring resource, use a little common sense when using frames. Don't use frames just for the sake of using them.