Due to time constraints, this tutorial only explains some practical knowledge, allowing you to move from the original table layout to the web standard (div css) layout, and use web standards to create common pages, which also achieves the purpose of this tutorial.
This tutorial is mostly explained step by step in the form of examples. The key points or difficulties involved in the examples will be explained, and the concepts will be less explained. Because concepts are difficult to explain clearly, or even if you explain them clearly, you may not be able to understand them, and even if you understand them, you may not be able to understand them. So I leave the concept to you to study in depth later.?