On HTML

Anyone know the code for takin' a pic, like say a Desktop image (any size) and makin' it the background for a web page so that the pic is sized to fit screen and not either show only the top 1/4 of the pic or have like 3 to 30 repets on the page when loaded??

I used this so far:

tried a few different desktop pics for Background="yadayada.jpg"
(IN place of bgcolor="black") in three different sizes. The smallest one put like 30 copys on screen. the 2nd one had like 1.5 and the 3rd(largest) you could only see the to left 1/4 of the pic !
I like all three desktop pics .. would use any of them .. if only I could get them to "fit Screen" o.0

Any ideas?