function changeImage() {
          newImage = "url(img/home2.jpg)";
          document.getElementById('back_home').style.backgroundImage = newImage;
}
function changeImage2() {
          newImage2 = "url(img/home3.jpg)";
          document.getElementById('back_home').style.backgroundImage = newImage2;
}
function changeImage3() {
          newImage2 = "url(img/home7.jpg)";
          document.getElementById('back_home').style.backgroundImage = newImage2;
}
function changeImage4() {
          newImage2 = "url(img/home5.jpg)";
          document.getElementById('back_home').style.backgroundImage = newImage2;
}
function changeImage5() {
          newImage2 = "url(img/back_home.jpg)";
          document.getElementById('back_home').style.backgroundImage = newImage2;
}
function changeImage6() {
          newImage2 = "url(img/home6.jpg)";
          document.getElementById('back_home').style.backgroundImage = newImage2;
}