Your background-image property's value is incorrect. It should be something like the following:
The link you provided has the following instead (note the brackets):
background-image: url ["http://.formationgrosman.com/images/background1.png"];
Which, I'll note, is not what you presented in your example above. When showing code, it's best to copy/paste your actual code rather than retyping it, because transcription errors like the one you introduced make finding the error difficult.