// pre-load main navigation rollover images

if (document.images) {

  mark_on = new Image(); mark_off = new Image(); 
  essa_on = new Image(); essa_off = new Image(); 
  cont_on = new Image(); cont_off = new Image(); 
  revs_on = new Image(); revs_off = new Image(); 
  phot_on = new Image(); phot_off = new Image(); 
  book_on = new Image(); book_off = new Image(); 
  gall_on = new Image(); gall_off = new Image(); 
  work_on = new Image(); work_off = new Image(); 


  mark_on.src = "../lib/img/nav/markOn.gif"; mark_off.src = "../lib/img/nav/markOff.gif";
  essa_on.src = "../lib/img/nav/essaOn.gif"; essa_off.src = "../lib/img/nav/essaOff.gif";
  cont_on.src = "../lib/img/nav/contOn.gif"; cont_off.src = "../lib/img/nav/contOff.gif";
  revs_on.src = "../lib/img/nav/revsOn.gif"; revs_off.src = "../lib/img/nav/revsOff.gif";
  phot_on.src = "../lib/img/nav/photOn.gif"; phot_off.src = "../lib/img/nav/photOff.gif";
  book_on.src = "../lib/img/nav/bookOn.gif"; book_off.src = "../lib/img/nav/bookOff.gif";
  gall_on.src = "../lib/img/nav/gallOn.gif"; gall_off.src = "../lib/img/nav/gallOff.gif";
  work_on.src = "../lib/img/nav/workOn.gif"; work_off.src = "../lib/img/nav/workOff.gif";
	
}

// rollover functions

function on(imageName) {
        if (document.images) document[imageName].src = eval(imageName + "_on.src");
}

function off(imageName) {
        if (document.images) document[imageName].src = eval(imageName + "_off.src");
}