Start it with
<style>
body {
background: #FFFFFF; <= this defines background color of the page.
color: #000000; <= The text color
}
You can create a custom element by making a section in the css.
Put the name where you would put body {,
with a dot in front of the name.
You can also give a background to something by putting url(link/to/image.gif); after the color code (you must drop the ; after the color).
Finally end the css with </style>.