var overIco = function(imgID) {
  document.getElementById(imgID).src = '../_img/layout/ico_'+imgID+'_over.png';
}

var outIco = function(imgID) {
  document.getElementById(imgID).src = '../_img/layout/ico_'+imgID+'_out.png';
}

var overPoster = function(year) {
  document.getElementById(year).src = '../_img/poster/poster'+year+'_hover.jpg'; 
}

var outPoster = function(year) {
  document.getElementById(year).src = '../_img/poster/poster'+year+'.jpg';
}