function pre_load_imgs()
{ (new Image()).src = "images/accueil_over_bkg.gif";
  (new Image()).src = "images/contact_over_bkg.gif";
  (new Image()).src = "images/plan_over_bkg.gif";
  (new Image()).src = "images/ok_over.gif";
}

function addLoadEvent(func)
{ var oldonload = window.onload;
  if(typeof window.onload != 'function') window.onload = func;
  else
  { window.onload = function()
    { if(oldonload) oldonload();
      func();
    }
  }
}

addLoadEvent(pre_load_imgs);