<html lang="en"> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta <title>Document</title> <style>. Box {width: 300px; /* width: 300px */ height: 300px; /* width 300px,px is pixel */ * background color */ background-color: red; */ /* 2 hexadecimal method :# FFFFF */ * 3 three primary color definition method: RGB (100,110,100) */ /* background-image: url(" image path "); /* Background-repeat: no-repeat; /* Background-repeat: no-repeat; /* background-repeat: repeat-x; /* background-repeat: repeat-y; */ /* Background-position: horizontal position vertical position; /* Horizontal position has three keywords: left; center; right; */ * The vertical position has three keywords :top; center; bottom; </style> </head> <body> <div class="box"> </div> </body> </ HTML >Copy the code