function bg(elem,color){
          if (elem){
          if (color) {
          elem.previousBackgroundColor = elem.style.backgroundColor;
          elem.style.backgroundColor = color;
          elem.onmouseout = resetBackground;
          }
          else if (elem.previousBackgroundColor){
          elem.style.backgroundColor = elem.previousBackgroundColor;
          }
          else {elem.style.backgroundColor = "transparent"}
          }
          }

          function resetBackground(){
          if (this){
          if (this.previousBackgroundColor){
          this.style.backgroundColor = this.previousBackgroundColor;
          }
          else (this.style.backgroundColor = "transparent");
          }
    }
          
          function changeImage(){
            arImages = new Array();

            arImages.push("4-workers-at-break.jpg");
            arImages.push("briefing-2-people.jpg");
            arImages.push("Diary-and-pencil.jpg");
            arImages.push("Freedom.jpg");
            arImages.push("Group-of-three-with-guy-at-.jpg");
            arImages.push("groups-studying-paper.jpg");
            arImages.push("Legs-and-notebook.jpg");
            arImages.push("Link.jpg");
            arImages.push("redhead-at-computer.jpg");
            arImages.push("Serious-couple-at-notebook.jpg");
            arImages.push("Smiling-group-with-blonde.jpg");
            arImages.push("Smiling-Group.jpg");
            arImages.push("Throwing-coat-in-air.jpg");
            arImages.push("Woman-on-rock-with-pc.jpg");

            document.getElementById("sideImage").src = imgFolder + arImages[Math.floor(Math.random()*arImages.length)];
          }