Answer:
We create a block div with an id="block" and we make the css code 
Step-by-step explanation:
<!doctype html> 
<html> 
<head> 
<meta charset="utf-8"> 
<title>bloque</title> 
<link href="bloque.css" rel="stylesheet" type="text/css"> 
</head> 
 
<body> 
 <!--we create the div with the id="block" and a text "hello world"--> 
 <div id="block"> hello world </div> 
 
</body> 
</html>
/* CSS Document */
/* we create the CSS file, then with the same id="block" we're programming in the CSS code*/
#block{
 background-color: #ECDEC9;
 padding: 20px;
 float: left;
 font-size: 50px;
 font-family: "Lucida Grande", "Lucida Sans Unicode", "Lucida Sans", "DejaVu Sans", "Verdana", "sans-serif"; 
}