HTML frame (Frameset) is a technology that displays multiple web pages on a single web page. It divides a web page into areas (or "frames"), each of which can display different web pages. This technology was very popular in the early Web era, but with the continuous development of network technology, it has been replaced by other technologies. HTML framework is implemented through a combination of frame elements, the main elements of which are , and . They are used to define the page structure, define subframes and embed external pages into the frame respectively. The element is the most important frame element, which defines the frame structure of the entire page. It has several important properties, such as rows, cols, and framespacing, which define the size, position, and spacing of each frame. Here is a simple example: In this example, the page is divided into several frames, with the top frame taking up 25% of the height from the top of the page and the bottom frame taking up 75%. The bottom frame is further divided into two columns, each taking up 50% of the width. Each frame has a corresponding src attribute that specifies the web page it wants to display. The element is used to define each subframe. It is usually nested inside the element and contains a src attribute and some other attributes, such as frameborder and scrolling, to control the frame's borders and scroll bars. Here's an example: In this example, defines a frame named "left" and specifies "left.html" as its content. The frameborder property sets whether the frame border is visible, and the scrolling property controls whether scroll bars are displayed inside the frame. The element is similar to and is used to embed another web page into the current web page. The main difference between it and is that can be nested anywhere, while must be inside a and can only be used in frame pages. Here is an example: In this example, embeds the "http://www.example.com" web page into the current web page and sets it to 100% width, 400px height. Although HTML framing technology was very popular in the past, its use is no longer recommended. This is because it has several disadvantages, such as: Framed page URLs and history can cause problems. Search engine optimization is difficult and it is difficult to optimize frame pages. Framed pages are considered an outdated technology and are no longer supported by many browsers. As a result, modern website developers have turned to other technologies such as responsive web design and single-page applications. In short, HTML frame technology is a technology that displays multiple web pages on a single web page. Although it was very popular in the past, it has now been replaced by other technologies. Regardless, it's still an important stage in the evolution of the Web and worth mentioning.