Like tacknut, I'm guessing it might be the path to the image relative to the stylesheet. Is the CSS in a separate text file in a sub-folder? If so, you need to dig up out of the sub-folder by proceeding the image path with 2dots slash ../img/javalogo.gif.
I don't have info about using quotes about the image name in background-image: url("img/javalogo.gif") -- the image path/name used to be unquoted in this usage, now I'm seeing examples where it is "quoted" (like a string used in the IMG tag, etc.) See http://www.w3schools.com/css/css_background.asp
Also not specifying background-repeat, just defaults to repeat tile.