background-repeat

The background-repeat property controls if, or how, a background picture tiles. You don’t often get a picture that exactly matches the size of the browser window. For example, if you change the size of the browser window, the browser rejigs the content to fit. If a picture is too small to fill the window, the browser repeats it over and over again to fill the window. This is known as tiling.

Some times tiling works a treat; it gives seamless repeating pattern that fills an area of any size. Sometimes, tiling looks awful. So, you can decide whether you want a picture to tile or not. If you do want to, you can tell the browser how to tile the picture.

Here’s an example that turns tiling off:

body {background-image: url("back.jpg"); 
      background-repeat: no-repeat;}

Your options are:

Use the value repeat-x to repeat the picture horizontally. The picture only appears once vertically, regardless of the height of the tag or window
Use the value repeat-y to repeat the picture vertically. The picture only appears once horizontally, regardless of the width of the tag or window
Repeat the picture in both directions (the default). Use the value repeat
Don’t repeat the picture. The picture displays once; it doesn’t tile. Use the value no-repeat