When I use your code and provide my own image it all seems to work. I would suggest checking the path to content_bg.jpg as well as spelling and capitalization.
If that doesn't help then, like coothead suggests, a link to the test site is always better since we don't have your images and there could be some error in the live code.
When posting code in the forum, please use the code tags, [code][/code] - available with the # button in the post edit window.
This will wrap your code in a scroll box which greatly helps the readability of your post.