var revert = new Array();
var inames = new Array('about','services', 'line','line1','portfolio','line2','resources','line3','contact');

if (document.images) { // Preload
  var flipped = new Array();
  for(i=0; i< inames.length; i++) {
    flipped[i] = new Image();
    flipped[i].src= "images/"+inames[i]+"_over.gif";
  }
}

function over(num) {
  if(document.images) {
    revert[num]=document.images[inames[num]].src;
    document.images[inames[num]].src= flipped[num].src;
  }
}
function out(num) {
  if(document.images) document.images[inames[num]].src= revert[num];
}