In XHTML tag elements, it can be roughly divided into three categories:

1. Block-level elements: such as h 1~h6, p, div, ul, table, etc. It has the nature of a block, can exist independently, is separated by line breaks, and belongs to a block-level element.

2. Top-level elements: html, body and frame are top-level elements, which behave like block-level elements and are also applicable to frame models.

3.Inline element: refers to the existence of other block-level elements, which are directly displayed between connected elements without line breaks. Commonly used inline elements are img, span, li, br, etc.