function addClass(id,new_class){
var i,n=0;
new_class=new_class.split(",");
for(i=0;i<new_class.length;i++){
if((" "+document.getElementById(id).className+" ").indexOf(" "+new_class[i]+" ")==-1){
document.getElementById(id).className+=" "+new_class[i];
n++;
}
}
return n;
}