分隔线

In other words, HTML tag represents element, and it becomes node in DOM, and becomes object in JavaScript.

遭遇到的js问题

Basic document flow

I am a basic block level element. My adjacent block level elements sit on new lines below me.

By default we span 100% of the width of our parent element, and we are as tall as our child content. Our total width and height is our content + padding + border width/height.

We are separated by our margins. Because of margin collapsing, we are separated by the width of one of our margins, not both.