Screen Resolution and Safari

[Che_Guava]

Hi. I am having trouble changing backgrounds dependant upon screen res in safari. This code works fine in IE, but safari does not like it for some reason:

function detect_resolution(){
 if ((screen.width>1152)||(screen.height>864)){
  document.getElementById("lb").background="Miscellany/border_left.gif";
  document.getElementById("rb").background="Miscellany/border_right.gif";
 }			
}

I am wondering if it is because this is called in the onload, or if it has to do with screen resolution.
Page in question: Garden Show.
Thanks very much in advance for any help with this .
~Che

[Pepejeria]

Try

document.getElementById("lb").style.backgroundImage = "url(myImage.gif)";