Changing the Background Header Image

Hello, I am trying to change the background header image with this http://www.cerencubukcu.com/wp-content/uploads/2013/04/headers.jpg and I added the below custom CSS code but I still don't see the image at the background. Can you please help me to fix it? Thanks. (my website: www.cerencubukcu.com) #header { background-image: url(‘http://cerencubukcu.com/wp-content/uploads/2013/04/headers.jpg’); }