background with a .jpg or .png file

How can i make the background extended dynamically ?
i used a .pjg file 1920x1200 pix but a part of my background is white (?)
i use style3

thx

You have to have large enough image, background images are not sizable, or you can do image repetition but that is used mostly for pattern backgrounds.

Hi,
ok, i've change the size. But a little problem remains :
why i have a blank space between by background and the top ? How to fix it.
my css is not changed :
body {
margin:0;
padding:0;
font-family:Tahoma, Geneva, sans-serif;
background-position:center top;
background-repeat:no-repeat;
}
thx

give us link so we can see

Hi Ivan,
i'm sorry but the site is on my localhost. Not uploaded yet.
i'll give it to you next time.
Many thanks for your help, you are very professional.