function changeImage(img){
var img_over = "images/" + img + "_o.png";
document.getElementById(img).src = img_over;
}
function changeImageBack(img){
var img_over = "images/" + img + ".png";
document.getElementById(img).src = img_over;
}
function changeImagejpg(img){
var img_over = "images/" + img + "_o.jpg";
document.getElementById(img).src = img_over;
}
function changeImageBackjpg(img){
var img_over = "images/" + img + ".jpg";
document.getElementById(img).src = img_over;
}