function change(num){
    for(var id = 1;id<=2;id++)
    {
    var dean="content"+id;
    if(id==num)
    document.getElementById(dean).style.display="block";
    else
    document.getElementById(dean).style.display="none";
    }
    if(num==1) 
    document.getElementById("change").className="hook bg1";
    if(num==2)
    document.getElementById("change").className="hook bg2";
    }