The first stage of html css questions

1. Write infrastructure html

2. Common inline elements: span, a, br, i, strong, q, cite, code, em ... block elements: div ,, p, h, ol, ul, dl, table, blockquote, from. .. inline block elements: input, img; 3. the known width and height div, horizontal and vertical center method:! [inserted here described image] (https://img-blog.csdnimg.cn/20200228153956439. png? x-oss-process = image / watermark, type_ZmFuZ3poZW5naGVpdGk, shadow_10, text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzcwNDAwNw ==, size_16, color_FFFFFF, t_70)

4. major browsers and kernel
first major browser must have their own core
IE Trident
Firefox Gecko
Goole Chrome Blink / WebKit
Safari WebKit
Opera Presto
5. single-label br, HR, Meta
6. three-column layout
Method One: Use the float ( to clear float)
HTML: Note that the left and right portions of the first, middle portion is then

CSS:

renderings:

Method two: position positioning (relative child parent Absolute)
the Html: this does not matter in the right-left order

Css:
Effect of FIG:

7. html css and writing a triangle
method: using a right triangle can be written only border

8. The parent element is a div, width and height is not fixed, the sub-element is a block element, the width and height are known, how the vertical and horizontal sub-element in the parent element is centered?
Analog third question;
Method a:
Method 2: Using flex layout