Here is a simple CSS file that you can use for a website:

/* Add a black background color to the body */

body {

  background-color: black;

}


/* Add a green text color to the heading */

h1 {

  color: green;

}


/* Add a red text color to the paragraph */

p {

  color: red;

}


/* Add a blue border to the image */

img {

  border: 2px solid blue;

}


/* Add some padding to the div element */

div {

  padding: 20px;

}

This CSS file adds a black background color to the body, a green color to the heading, a red color to the paragraph, a blue border to the image, and some padding to the div element. You can use this as a starting point and customize it to suit your needs.