Usually frameset have equal count of columns and rows but a frame structure with an irregular number of columns and rows can be made by nesting two or more framesets as shown the frame layout needs two frameset A and B having two frames in them and not with a single frameset.
The syntax for the above is shown as
The code for nested frames is similar to any other nested tags. But it becomes confusing with nested frames. Nesting can be avoided by referencing other web page with frames, by embedding the frames in the current web page.
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