Background width

Hey Sakin, Quick question, I changed the background of my website. See here an example: http://www.worldfootballguide.com/2015-asian-cup-kicks-january/ I see the background doesn't fill the entire width of the screen between header and footer. So on the left and right side you stil see a grey colour. Is this normal or is there something wrong with the background settings? Thanks in advance Joao