This elements mainly stands for specifying the frames of a window.One frameset contain different frames. A frameset requires a special frameset-specific doctype, and does not allow for any content inside the body of the page.Or in other words The frameset element is a frame container for dividing a window into rectangular subspaces called frames. In a Frameset document, the outermost frameset element takes the place of BODY and immediately follows the HEAD.
The <frameset> Tag
HTML5 doesn't support this tag.This tag specifies how many frames are there for dividing one window, and also about its width and height etc. FRAMESET tags and the subsequent FRAMEs are set up in the <head> of your document, not in the body. It is not necessary to have anything in the body at all.
Frameset Syntax And Attribute Specification
Syntax for frameset is,
<frameset> . . . </frameset>
Attribute specifications for frameset is,
ROWS=MultiLengths (row lengths)
COLS=MultiLengths (column lengths)
ONLOAD=Script (all frames have been loaded)
ONUNLOAD=Script (all frames have been removed)