1: Frameset and iframe is a frame tag, indicating that the web page document is composed of frames, and sets the layout of the frames that make up the frameset in the document, which is used to divide the frames. Each Frames are marked by . is used to set the properties of each frame that makes up the frame set. must be used within . Note: The frame order of tags is from left to right or top to bottom. Iframe is the abbreviation of Inline Frame, which is called inline frame. It is like a brother to frame. Frame is a frame mark, and Iframe is called a floating frame mark. The biggest feature of it different from the Frame mark is that the HTML file referenced by this mark is not displayed independently from other HTML files, but can be directly embedded in an HTML file, together with this The contents of HTML files are integrated with each other and become a whole; because it can display the same content multiple times on a page without having to write the content repeatedly, people call this effect "picture-in-picture".