Background Fixed Please

So I am trying to make my background fixed. For the life of me can not figure it out, and I thought I was doing it right as well.

So I am using the Aurora Theme and just having some problems with it being static/fixed.

Here is the code I got.

html{background-image:url('tile.gif'); background-repeat:yes-repeat background-attachment:fixed; font-family:Tahoma, Arial, Helvetica, sans-serif}
#wrapper{margin:0px auto; margin-top:20px;background-color:#181B19; width:975px; border:1px solid #383C37;
font-family: 'Trebuchet MS', Tahoma, Arial, Helvetica, sans-serif;
font-size:0.7em;
line-height:1.4em;}