Headings

• Headings (h1 through h6 elements) are workhorse tags that help provide structure and labeling to your content.
• The heading tags in a webpage need to go in order and indicate the hierarchical relationships of your content.
• Headings with equal (or higher) rank start new implied sections, headings with lower rank start subsections of the previous one.
• Each page should always have one (and only one) h1 element, which is the main subject of your content.

参考资料：

• Use Headings to Show Hierarchical Relationships of Content