Basic terminology in CSS

1. Document Flow: The default arrangement of page elements, according to the order of elements in the HTML document, from left to right, from top to bottom;

2. Block elements: The default is a row, in the vertical direction, you can set the width and height, such as:<div>,<p>,

3. Inline elements: By default in a row horizontally, width and height determined by the content, cannot be set, such as <span><a><em>...;

4. Replace element: element content is set by the attribute of the tag, which is actually a placeholder, for example <input type= "" >

5. Non-replacement elements: element content is included in the current label, e.g. <p>,

6. How do I differentiate between replacement and non-replacement elements?

6-1. Replace element because the element content comes from external resources, most need only one label, because the single label is more, but there are exceptions, such as:

<video><script><video>, ..... Most of these tags have src, which indicates the resource path to be introduced. If the contents of the label are either invalid,

Or it's just a resource introduction.

6-2. Non-replacement elements, the content of which is written directly by the user in the label, such as <p>,

<! DOCTYPE html>