A frame document contains no displayable content, except perhaps a message for nonframe enabled browsers (see noframes later in this chapter).
Rather,
<FRAME> tags inside the one or more
frameset tags, which encapsulate the contents of a
frame document, provide URL references to the
individual documents that occupy each frame.
The frame tag appears only within a frameset. Use it to set, via its associated src attribute, the URL of the document content that initially gets displayed inside the respective frame.
Frames are placed into a frameset column by column, from left to right, and then row by row, from top to bottom, so the sequence and number of frame tags inside the frameset tag are important.