Cant delete background colour!

Im trying to make the backgrounf picture full the background but it wont there is always white around it and tis annoying me im editing it in admin panel under colours clicking save and it just puts the code back help

*Bump i get this problem too, i've seen my background image appear few times but it is mainly the non image white back that loads... my members say on there side they get the image tiled as its supposed to be. but for me it doesn't work... EPIC FAIL

- when it has worked i duno what i did to get it to work

- I hav downloaded IE8 and Firefox to check if its my browser and no luck
- Also deleted previous cookies

kk, i got mine workin...

Code:

/*Defaults*/
body {
   margin: 0 auto;
   background-image: url('http://hitskin.com/themes/13/20/92/i_background.png');
   background-attachment: scroll;
   font-family: Arial,Verdana,Tahoma,sans-serif;
   font-size: 12px;
   line-height: 135%;
   }

heres the bit i edited... i took out ALL the colour in this bit and put in the exact URL for the image now it loads for me, obviously this may not be the case for you as you probs have a different CSS, but this was up the very top and u should be able to see the "Body" to edit

hope this helps