Repeat-x and Repeat-y

Can someone give me an example of how repeat-x and/or 
repeat-y should work? I don't see any examples, and I'm
not sure what the syntax would be in the long string.
Can I specify both repeat-x and repeat-y or must I 
specify both. 

For example, what if I want to repeat an image twice down
the left side of the screen and have it fixed (so that something
on the background lines up with text)?


Mary Morris