module 6

 div position: sticky, absolute and telative, fixed

z-index: 1 ; it will show forward to another picture, which z index is greater , their image come first if they are emerged.

h3::before / after === they mainly work in adding elements to all.

p::first letter,/ first line

::selection makes mouse selection  design.

button onclick: welcome

script tag: function welcome()

{ alert(":");}

.row> div{ flex; 1;}